[PATCH V5 3/4] drm/bridge: Add driver for GE B850v3 LVDS/DP++ Bridge

[Archit Taneja]

On 09/26/2016 05:24 PM, Peter Senna Tschudin wrote:
>
> On Monday, September 26, 2016 12:29 CEST, Archit Taneja  codeaurora.org> wrote:
>
>> Hi,
>>
>> Some comments.
>
> Thank you for the review!
>
>>
>> On 08/09/2016 10:11 PM, Peter Senna Tschudin wrote:
>>> Add a driver that create a drm_bridge and a drm_connector for the LVDS
>>> to DP++ display bridge of the GE B850v3.
>>>
>>> There are two physical bridges on the video signal pipeline: a
>>> STDP4028(LVDS to DP) and a STDP2690(DP to DP++).  The hardware and
>>> firmware made it complicated for this binding to comprise two device
>>> tree nodes, as the design goal is to configure both bridges based on
>>> the LVDS signal, which leave the driver powerless to control the video
>>> processing pipeline. The two bridges behaves as a single bridge, and
>>> the driver is only needed for telling the host about EDID / HPD, and
>>> for giving the host powers to ack interrupts. The video signal pipeline
>>> is as follows:
>>>
>>>   Host -> LVDS|--(STDP4028)--|DP -> DP|--(STDP2690)--|DP++ -> Video output
>>>
>>> Cc: Martyn Welch 
>>> Cc: Martin Donnelly 
>>> Cc: Daniel Vetter 
>>> Cc: Enric Balletbo i Serra 
>>> Cc: Philipp Zabel 
>>> Cc: Rob Herring 
>>> Cc: Fabio Estevam 
>>> CC: David Airlie 
>>> CC: Thierry Reding 
>>> CC: Thierry Reding 
>>> Reviewed-by: Enric Balletbo 
>>> Signed-off-by: Peter Senna Tschudin 
>>> ---
>>> Changes from V4:
>>>  - Check the output of the first call to i2c_smbus_write_word_data() and 
>>> return
>>>it's error code for failing gracefully on i2c issues
>>>  - Renamed the i2c_driver.name from "ge,b850v3-lvds-dp" to "b850v3-lvds-dp" 
>>> to
>>>remove the comma from the driver name
>>>
>>> Changes from V3:
>>>  - 3/4 instead of 4/5
>>>  - Tested on next-20160804
>>>
>>> Changes from V2:
>>>  - Made it atomic to be applied on next-20160729 on top of Liu Ying changes
>>>that made imx-ldb atomic
>>>
>>> Changes from V1:
>>>  - New commit message
>>>  - Removed 3 empty entry points
>>>  - Removed memory leak from ge_b850v3_lvds_dp_get_modes()
>>>  - Added a lock for mode setting
>>>  - Removed a few blank lines
>>>  - Changed the order at Makefile and Kconfig
>>>
>>>  MAINTAINERS|   8 +
>>>  drivers/gpu/drm/bridge/Kconfig |  11 +
>>>  drivers/gpu/drm/bridge/Makefile|   1 +
>>>  drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c | 405 
>>> +
>>>  4 files changed, 425 insertions(+)
>>>  create mode 100644 drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
>>>
>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>> index a306795..e8d106a 100644
>>> --- a/MAINTAINERS
>>> +++ b/MAINTAINERS
>>> @@ -5142,6 +5142,14 @@ W:   https://linuxtv.org
>>>  S: Maintained
>>>  F: drivers/media/radio/radio-gemtek*
>>>
>>> +GENERAL ELECTRIC B850V3 LVDS/DP++ BRIDGE
>>> +M: Peter Senna Tschudin 
>>> +M: Martin Donnelly 
>>> +M: Martyn Welch 
>>> +S: Maintained
>>> +F: drivers/gpu/drm/bridge/ge_b850v3_dp2.c
>>> +F: Documentation/devicetree/bindings/ge/b850v3_dp2_bridge.txt
>>> +
>>>  GENERIC GPIO I2C DRIVER
>>>  M: Haavard Skinnemoen 
>>>  S: Supported
>>
>> Could you move the MAINTAINERS change to a different patch? It would
>> make it easier to integrate separately.
>
> If needed, yes sure.
>
>>
>>> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
>>> index b590e67..b4b70fb 100644
>>> --- a/drivers/gpu/drm/bridge/Kconfig
>>> +++ b/drivers/gpu/drm/bridge/Kconfig
>>> @@ -32,6 +32,17 @@ config DRM_DW_HDMI_AHB_AUDIO
>>>   Designware HDMI block.  This is used in conjunction with
>>>   the i.MX6 HDMI driver.
>>>
>>> +config DRM_GE_B850V3_LVDS_DP
>>> +   tristate "GE B850v3 LVDS to DP++ display bridge"
>>> +   depends on OF
>>> +   select DRM_KMS_HELPER
>>> +   select DRM_PANEL
>>> +   ---help---
>>> +  This is a driver for the display bridge of
>>> +  GE B850v3 that convert dual channel LVDS
>>> +  to DP++. This is used with the i.MX6 imx-ldb
>>> +  driver.
>>> +
>>>  config DRM_NXP_PTN3460
>>> tristate "NXP PTN3460 DP/LVDS bridge"
>>> depends on OF
>>> diff --git a/drivers/gpu/drm/bridge/Makefile 
>>> b/drivers/gpu/drm/bridge/Makefile
>>> index efdb07e..b9606f3 100644
>>> --- a/drivers/gpu/drm/bridge/Makefile
>>> +++ b/drivers/gpu/drm/bridge/Makefile
>>> @@ -3,6 +3,7 @@ ccflags-y := -Iinclude/drm
>>>  obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
>>>  obj-$(CONFIG_DRM_DW_HDMI) += dw-hdmi.o
>>>  obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
>>> +obj-$(CONFIG_DRM_GE_B850V3_LVDS_DP) += ge_b850v3_lvds_dp.o
>>>  obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
>>>  obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
>>>  obj-$(CONFIG_DRM_SII902X) += sii902x.o
>>> diff --git a/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c 
>>> b/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
>>> new file mode 100644
>>> index 000..81e9279
>>> --- /dev/null
>>> +++ b/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
>>> @@ -0,0 

[PATCH V5 3/4] drm/bridge: Add driver for GE B850v3 LVDS/DP++ Bridge

[Archit Taneja]

Hi,

Some comments.

On 08/09/2016 10:11 PM, Peter Senna Tschudin wrote:
> Add a driver that create a drm_bridge and a drm_connector for the LVDS
> to DP++ display bridge of the GE B850v3.
>
> There are two physical bridges on the video signal pipeline: a
> STDP4028(LVDS to DP) and a STDP2690(DP to DP++).  The hardware and
> firmware made it complicated for this binding to comprise two device
> tree nodes, as the design goal is to configure both bridges based on
> the LVDS signal, which leave the driver powerless to control the video
> processing pipeline. The two bridges behaves as a single bridge, and
> the driver is only needed for telling the host about EDID / HPD, and
> for giving the host powers to ack interrupts. The video signal pipeline
> is as follows:
>
>   Host -> LVDS|--(STDP4028)--|DP -> DP|--(STDP2690)--|DP++ -> Video output
>
> Cc: Martyn Welch 
> Cc: Martin Donnelly 
> Cc: Daniel Vetter 
> Cc: Enric Balletbo i Serra 
> Cc: Philipp Zabel 
> Cc: Rob Herring 
> Cc: Fabio Estevam 
> CC: David Airlie 
> CC: Thierry Reding 
> CC: Thierry Reding 
> Reviewed-by: Enric Balletbo 
> Signed-off-by: Peter Senna Tschudin 
> ---
> Changes from V4:
>  - Check the output of the first call to i2c_smbus_write_word_data() and 
> return
>it's error code for failing gracefully on i2c issues
>  - Renamed the i2c_driver.name from "ge,b850v3-lvds-dp" to "b850v3-lvds-dp" to
>remove the comma from the driver name
>
> Changes from V3:
>  - 3/4 instead of 4/5
>  - Tested on next-20160804
>
> Changes from V2:
>  - Made it atomic to be applied on next-20160729 on top of Liu Ying changes
>that made imx-ldb atomic
>
> Changes from V1:
>  - New commit message
>  - Removed 3 empty entry points
>  - Removed memory leak from ge_b850v3_lvds_dp_get_modes()
>  - Added a lock for mode setting
>  - Removed a few blank lines
>  - Changed the order at Makefile and Kconfig
>
>  MAINTAINERS|   8 +
>  drivers/gpu/drm/bridge/Kconfig |  11 +
>  drivers/gpu/drm/bridge/Makefile|   1 +
>  drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c | 405 
> +
>  4 files changed, 425 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a306795..e8d106a 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5142,6 +5142,14 @@ W: https://linuxtv.org
>  S:   Maintained
>  F:   drivers/media/radio/radio-gemtek*
>
> +GENERAL ELECTRIC B850V3 LVDS/DP++ BRIDGE
> +M:   Peter Senna Tschudin 
> +M:   Martin Donnelly 
> +M:   Martyn Welch 
> +S:   Maintained
> +F:   drivers/gpu/drm/bridge/ge_b850v3_dp2.c
> +F:   Documentation/devicetree/bindings/ge/b850v3_dp2_bridge.txt
> +
>  GENERIC GPIO I2C DRIVER
>  M:   Haavard Skinnemoen 
>  S:   Supported

Could you move the MAINTAINERS change to a different patch? It would 
make it easier to integrate separately.

> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index b590e67..b4b70fb 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -32,6 +32,17 @@ config DRM_DW_HDMI_AHB_AUDIO
> Designware HDMI block.  This is used in conjunction with
> the i.MX6 HDMI driver.
>
> +config DRM_GE_B850V3_LVDS_DP
> + tristate "GE B850v3 LVDS to DP++ display bridge"
> + depends on OF
> + select DRM_KMS_HELPER
> + select DRM_PANEL
> + ---help---
> +  This is a driver for the display bridge of
> +  GE B850v3 that convert dual channel LVDS
> +  to DP++. This is used with the i.MX6 imx-ldb
> +  driver.
> +
>  config DRM_NXP_PTN3460
>   tristate "NXP PTN3460 DP/LVDS bridge"
>   depends on OF
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index efdb07e..b9606f3 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -3,6 +3,7 @@ ccflags-y := -Iinclude/drm
>  obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
>  obj-$(CONFIG_DRM_DW_HDMI) += dw-hdmi.o
>  obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
> +obj-$(CONFIG_DRM_GE_B850V3_LVDS_DP) += ge_b850v3_lvds_dp.o
>  obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
>  obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
>  obj-$(CONFIG_DRM_SII902X) += sii902x.o
> diff --git a/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c 
> b/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
> new file mode 100644
> index 000..81e9279
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
> @@ -0,0 +1,405 @@
> +/*
> + * Driver for GE B850v3 DP display bridge
> +
> + * Copyright (c) 2016, Collabora Ltd.
> + * Copyright (c) 2016, General Electric Company
> +
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> +
> + * This program is distributed in the hope it 

[PATCH V5 3/4] drm/bridge: Add driver for GE B850v3 LVDS/DP++ Bridge

[Archit Taneja]

Hi,

On 09/26/2016 02:28 PM, Peter Senna Tschudin wrote:
>  Hi Archit,
>
> On Monday, September 26, 2016 10:31 CEST, Archit Taneja  codeaurora.org> wrote:
>
>> Hi Peter,
>>
>> On 09/26/2016 01:57 PM, Peter Senna Tschudin wrote:
>>> Patch 1/4 is already on linux-next, but what about this one? Ping?
>
>>
>> I'd posted some queries a couple of times which you didn't answer to.
>> Could you please respond to them before we try to get this merged?
>
> Your queries were already answered by similar questions. The commit messages 
> and cover letter also addresses the design decisions of the code. But 
> basically the driver usefulness to other scenarios is severely limited by the 
> firmware used by both chips. And when using the firmware that goes with this 
> specific hardware, then yes, the two chips are always expected to work 
> together. But the main point is that with the custom firmware each chip do 
> not behave as independent bridges anymore.

Thanks for the reply.

It wasn't entirely clear from the commit message that a custom firmware
was exclusively used on this board to program these chips in order to
get these 2 working together.

I browsed the earlier versions of the patch and saw you explained
the same thing to someone else. Sorry about that, I missed reading
that before.

Could you please specify this explicitly in the commit message? Perhaps,
also mention that there is an external microcontroller with a custom
firmware that manages most of the video operations. For the sake of
completeness, could you also mention the part name of the controller
that's running this firmware?

Also, in the comments in the beginning of the driver:

"However the physical bridges are automatically configured by the input 
video signal, and the driver has no access to the video processing 
pipeline."

Is the automatic configuration done by the firmware, or is it a
feature of the chips itself?

>
> On the other side, I was careful to use meaningful names for the registers, 
> so a future implementation based on same chips can take the basics from this 
> work, at least as a starting point.

Thanks, that would be handy for later.

I had some comments on the code. I'll share those in another reply.

Archit

>
> Thanks,
>
> Peter
>

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH V5 3/4] drm/bridge: Add driver for GE B850v3 LVDS/DP++ Bridge

[Archit Taneja]

Hi Peter,

On 09/26/2016 01:57 PM, Peter Senna Tschudin wrote:
> Patch 1/4 is already on linux-next, but what about this one? Ping?

I'd posted some queries a couple of times which you didn't answer to.
Could you please respond to them before we try to get this merged?

Archit

>
> On Tuesday, August 9, 2016 18:41 CEST, Peter Senna Tschudin  collabora.com> wrote:
>
>> Add a driver that create a drm_bridge and a drm_connector for the LVDS
>> to DP++ display bridge of the GE B850v3.
>>
>> There are two physical bridges on the video signal pipeline: a
>> STDP4028(LVDS to DP) and a STDP2690(DP to DP++).  The hardware and
>> firmware made it complicated for this binding to comprise two device
>> tree nodes, as the design goal is to configure both bridges based on
>> the LVDS signal, which leave the driver powerless to control the video
>> processing pipeline. The two bridges behaves as a single bridge, and
>> the driver is only needed for telling the host about EDID / HPD, and
>> for giving the host powers to ack interrupts. The video signal pipeline
>> is as follows:
>>
>>   Host -> LVDS|--(STDP4028)--|DP -> DP|--(STDP2690)--|DP++ -> Video output
>>
>> Cc: Martyn Welch 
>> Cc: Martin Donnelly 
>> Cc: Daniel Vetter 
>> Cc: Enric Balletbo i Serra 
>> Cc: Philipp Zabel 
>> Cc: Rob Herring 
>> Cc: Fabio Estevam 
>> CC: David Airlie 
>> CC: Thierry Reding 
>> CC: Thierry Reding 
>> Reviewed-by: Enric Balletbo 
>> Signed-off-by: Peter Senna Tschudin 
>> ---
>> Changes from V4:
>>  - Check the output of the first call to i2c_smbus_write_word_data() and 
>> return
>>it's error code for failing gracefully on i2c issues
>>  - Renamed the i2c_driver.name from "ge,b850v3-lvds-dp" to "b850v3-lvds-dp" 
>> to
>>remove the comma from the driver name
>>
>> Changes from V3:
>>  - 3/4 instead of 4/5
>>  - Tested on next-20160804
>>
>> Changes from V2:
>>  - Made it atomic to be applied on next-20160729 on top of Liu Ying changes
>>that made imx-ldb atomic
>>
>> Changes from V1:
>>  - New commit message
>>  - Removed 3 empty entry points
>>  - Removed memory leak from ge_b850v3_lvds_dp_get_modes()
>>  - Added a lock for mode setting
>>  - Removed a few blank lines
>>  - Changed the order at Makefile and Kconfig
>>
>>  MAINTAINERS|   8 +
>>  drivers/gpu/drm/bridge/Kconfig |  11 +
>>  drivers/gpu/drm/bridge/Makefile|   1 +
>>  drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c | 405 
>> +
>>  4 files changed, 425 insertions(+)
>>  create mode 100644 drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index a306795..e8d106a 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -5142,6 +5142,14 @@ W:https://linuxtv.org
>>  S:  Maintained
>>  F:  drivers/media/radio/radio-gemtek*
>>
>> +GENERAL ELECTRIC B850V3 LVDS/DP++ BRIDGE
>> +M:  Peter Senna Tschudin 
>> +M:  Martin Donnelly 
>> +M:  Martyn Welch 
>> +S:  Maintained
>> +F:  drivers/gpu/drm/bridge/ge_b850v3_dp2.c
>> +F:  Documentation/devicetree/bindings/ge/b850v3_dp2_bridge.txt
>> +
>>  GENERIC GPIO I2C DRIVER
>>  M:  Haavard Skinnemoen 
>>  S:  Supported
>> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
>> index b590e67..b4b70fb 100644
>> --- a/drivers/gpu/drm/bridge/Kconfig
>> +++ b/drivers/gpu/drm/bridge/Kconfig
>> @@ -32,6 +32,17 @@ config DRM_DW_HDMI_AHB_AUDIO
>>Designware HDMI block.  This is used in conjunction with
>>the i.MX6 HDMI driver.
>>
>> +config DRM_GE_B850V3_LVDS_DP
>> +tristate "GE B850v3 LVDS to DP++ display bridge"
>> +depends on OF
>> +select DRM_KMS_HELPER
>> +select DRM_PANEL
>> +---help---
>> +  This is a driver for the display bridge of
>> +  GE B850v3 that convert dual channel LVDS
>> +  to DP++. This is used with the i.MX6 imx-ldb
>> +  driver.
>> +
>>  config DRM_NXP_PTN3460
>>  tristate "NXP PTN3460 DP/LVDS bridge"
>>  depends on OF
>> diff --git a/drivers/gpu/drm/bridge/Makefile 
>> b/drivers/gpu/drm/bridge/Makefile
>> index efdb07e..b9606f3 100644
>> --- a/drivers/gpu/drm/bridge/Makefile
>> +++ b/drivers/gpu/drm/bridge/Makefile
>> @@ -3,6 +3,7 @@ ccflags-y := -Iinclude/drm
>>  obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
>>  obj-$(CONFIG_DRM_DW_HDMI) += dw-hdmi.o
>>  obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
>> +obj-$(CONFIG_DRM_GE_B850V3_LVDS_DP) += ge_b850v3_lvds_dp.o
>>  obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
>>  obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
>>  obj-$(CONFIG_DRM_SII902X) += sii902x.o
>> diff --git a/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c 
>> b/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
>> new file mode 100644
>> index 000..81e9279
>> --- /dev/null
>> +++ b/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
>> @@ -0,0 +1,405 @@
>> +/*
>> + * Driver for GE B850v3 DP display bridge
>> +
>> + * Copyright (c) 2016, Collabora Ltd.
>> + * Copyright (c) 2016, 

Re: [PATCH V5 3/4] drm/bridge: Add driver for GE B850v3 LVDS/DP++ Bridge

[Peter Senna Tschudin]

On Monday, September 26, 2016 12:29 CEST, Archit Taneja  wrote: 

> Hi,
> 
> Some comments.

Thank you for the review!

> 
> On 08/09/2016 10:11 PM, Peter Senna Tschudin wrote:
> > Add a driver that create a drm_bridge and a drm_connector for the LVDS
> > to DP++ display bridge of the GE B850v3.
> >
> > There are two physical bridges on the video signal pipeline: a
> > STDP4028(LVDS to DP) and a STDP2690(DP to DP++).  The hardware and
> > firmware made it complicated for this binding to comprise two device
> > tree nodes, as the design goal is to configure both bridges based on
> > the LVDS signal, which leave the driver powerless to control the video
> > processing pipeline. The two bridges behaves as a single bridge, and
> > the driver is only needed for telling the host about EDID / HPD, and
> > for giving the host powers to ack interrupts. The video signal pipeline
> > is as follows:
> >
> >   Host -> LVDS|--(STDP4028)--|DP -> DP|--(STDP2690)--|DP++ -> Video output
> >
> > Cc: Martyn Welch 
> > Cc: Martin Donnelly 
> > Cc: Daniel Vetter 
> > Cc: Enric Balletbo i Serra 
> > Cc: Philipp Zabel 
> > Cc: Rob Herring 
> > Cc: Fabio Estevam 
> > CC: David Airlie 
> > CC: Thierry Reding 
> > CC: Thierry Reding 
> > Reviewed-by: Enric Balletbo 
> > Signed-off-by: Peter Senna Tschudin 
> > ---
> > Changes from V4:
> >  - Check the output of the first call to i2c_smbus_write_word_data() and 
> > return
> >it's error code for failing gracefully on i2c issues
> >  - Renamed the i2c_driver.name from "ge,b850v3-lvds-dp" to "b850v3-lvds-dp" 
> > to
> >remove the comma from the driver name
> >
> > Changes from V3:
> >  - 3/4 instead of 4/5
> >  - Tested on next-20160804
> >
> > Changes from V2:
> >  - Made it atomic to be applied on next-20160729 on top of Liu Ying changes
> >that made imx-ldb atomic
> >
> > Changes from V1:
> >  - New commit message
> >  - Removed 3 empty entry points
> >  - Removed memory leak from ge_b850v3_lvds_dp_get_modes()
> >  - Added a lock for mode setting
> >  - Removed a few blank lines
> >  - Changed the order at Makefile and Kconfig
> >
> >  MAINTAINERS|   8 +
> >  drivers/gpu/drm/bridge/Kconfig |  11 +
> >  drivers/gpu/drm/bridge/Makefile|   1 +
> >  drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c | 405 
> > +
> >  4 files changed, 425 insertions(+)
> >  create mode 100644 drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index a306795..e8d106a 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -5142,6 +5142,14 @@ W:   https://linuxtv.org
> >  S: Maintained
> >  F: drivers/media/radio/radio-gemtek*
> >
> > +GENERAL ELECTRIC B850V3 LVDS/DP++ BRIDGE
> > +M: Peter Senna Tschudin 
> > +M: Martin Donnelly 
> > +M: Martyn Welch 
> > +S: Maintained
> > +F: drivers/gpu/drm/bridge/ge_b850v3_dp2.c
> > +F: Documentation/devicetree/bindings/ge/b850v3_dp2_bridge.txt
> > +
> >  GENERIC GPIO I2C DRIVER
> >  M: Haavard Skinnemoen 
> >  S: Supported
> 
> Could you move the MAINTAINERS change to a different patch? It would 
> make it easier to integrate separately.

If needed, yes sure.

> 
> > diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> > index b590e67..b4b70fb 100644
> > --- a/drivers/gpu/drm/bridge/Kconfig
> > +++ b/drivers/gpu/drm/bridge/Kconfig
> > @@ -32,6 +32,17 @@ config DRM_DW_HDMI_AHB_AUDIO
> >   Designware HDMI block.  This is used in conjunction with
> >   the i.MX6 HDMI driver.
> >
> > +config DRM_GE_B850V3_LVDS_DP
> > +   tristate "GE B850v3 LVDS to DP++ display bridge"
> > +   depends on OF
> > +   select DRM_KMS_HELPER
> > +   select DRM_PANEL
> > +   ---help---
> > +  This is a driver for the display bridge of
> > +  GE B850v3 that convert dual channel LVDS
> > +  to DP++. This is used with the i.MX6 imx-ldb
> > +  driver.
> > +
> >  config DRM_NXP_PTN3460
> > tristate "NXP PTN3460 DP/LVDS bridge"
> > depends on OF
> > diff --git a/drivers/gpu/drm/bridge/Makefile 
> > b/drivers/gpu/drm/bridge/Makefile
> > index efdb07e..b9606f3 100644
> > --- a/drivers/gpu/drm/bridge/Makefile
> > +++ b/drivers/gpu/drm/bridge/Makefile
> > @@ -3,6 +3,7 @@ ccflags-y := -Iinclude/drm
> >  obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
> >  obj-$(CONFIG_DRM_DW_HDMI) += dw-hdmi.o
> >  obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
> > +obj-$(CONFIG_DRM_GE_B850V3_LVDS_DP) += ge_b850v3_lvds_dp.o
> >  obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
> >  obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
> >  obj-$(CONFIG_DRM_SII902X) += sii902x.o
> > diff --git a/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c 
> > b/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
> > new file mode 100644
> > index 000..81e9279
> > --- /dev/null
> > +++ b/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
> > @@ -0,0 +1,405 @@
> > +/*
> > + * Driver for GE B850v3 DP display bridge
> > +
> > + * 

Re: [PATCH V5 3/4] drm/bridge: Add driver for GE B850v3 LVDS/DP++ Bridge

[Peter Senna Tschudin]

 Hi Archit,

On Monday, September 26, 2016 10:31 CEST, Archit Taneja  wrote: 

> Hi Peter,
> 
> On 09/26/2016 01:57 PM, Peter Senna Tschudin wrote:
> > Patch 1/4 is already on linux-next, but what about this one? Ping?
> 
> I'd posted some queries a couple of times which you didn't answer to.
> Could you please respond to them before we try to get this merged?

Your queries were already answered by similar questions. The commit messages 
and cover letter also addresses the design decisions of the code. But basically 
the driver usefulness to other scenarios is severely limited by the firmware 
used by both chips. And when using the firmware that goes with this specific 
hardware, then yes, the two chips are always expected to work together. But the 
main point is that with the custom firmware each chip do not behave as 
independent bridges anymore.

On the other side, I was careful to use meaningful names for the registers, so 
a future implementation based on same chips can take the basics from this work, 
at least as a starting point.

Thanks,

Peter

Re: [PATCH V5 3/4] drm/bridge: Add driver for GE B850v3 LVDS/DP++ Bridge

[Peter Senna Tschudin]

Patch 1/4 is already on linux-next, but what about this one? Ping?

On Tuesday, August 9, 2016 18:41 CEST, Peter Senna Tschudin  wrote: 

> Add a driver that create a drm_bridge and a drm_connector for the LVDS
> to DP++ display bridge of the GE B850v3.
> 
> There are two physical bridges on the video signal pipeline: a
> STDP4028(LVDS to DP) and a STDP2690(DP to DP++).  The hardware and
> firmware made it complicated for this binding to comprise two device
> tree nodes, as the design goal is to configure both bridges based on
> the LVDS signal, which leave the driver powerless to control the video
> processing pipeline. The two bridges behaves as a single bridge, and
> the driver is only needed for telling the host about EDID / HPD, and
> for giving the host powers to ack interrupts. The video signal pipeline
> is as follows:
> 
>   Host -> LVDS|--(STDP4028)--|DP -> DP|--(STDP2690)--|DP++ -> Video output
> 
> Cc: Martyn Welch 
> Cc: Martin Donnelly 
> Cc: Daniel Vetter 
> Cc: Enric Balletbo i Serra 
> Cc: Philipp Zabel 
> Cc: Rob Herring 
> Cc: Fabio Estevam 
> CC: David Airlie 
> CC: Thierry Reding 
> CC: Thierry Reding 
> Reviewed-by: Enric Balletbo 
> Signed-off-by: Peter Senna Tschudin 
> ---
> Changes from V4:
>  - Check the output of the first call to i2c_smbus_write_word_data() and 
> return
>it's error code for failing gracefully on i2c issues
>  - Renamed the i2c_driver.name from "ge,b850v3-lvds-dp" to "b850v3-lvds-dp" to
>remove the comma from the driver name
> 
> Changes from V3:
>  - 3/4 instead of 4/5
>  - Tested on next-20160804
> 
> Changes from V2:
>  - Made it atomic to be applied on next-20160729 on top of Liu Ying changes
>that made imx-ldb atomic
> 
> Changes from V1:
>  - New commit message
>  - Removed 3 empty entry points
>  - Removed memory leak from ge_b850v3_lvds_dp_get_modes()
>  - Added a lock for mode setting
>  - Removed a few blank lines
>  - Changed the order at Makefile and Kconfig
> 
>  MAINTAINERS|   8 +
>  drivers/gpu/drm/bridge/Kconfig |  11 +
>  drivers/gpu/drm/bridge/Makefile|   1 +
>  drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c | 405 
> +
>  4 files changed, 425 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a306795..e8d106a 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5142,6 +5142,14 @@ W: https://linuxtv.org
>  S:   Maintained
>  F:   drivers/media/radio/radio-gemtek*
>  
> +GENERAL ELECTRIC B850V3 LVDS/DP++ BRIDGE
> +M:   Peter Senna Tschudin 
> +M:   Martin Donnelly 
> +M:   Martyn Welch 
> +S:   Maintained
> +F:   drivers/gpu/drm/bridge/ge_b850v3_dp2.c
> +F:   Documentation/devicetree/bindings/ge/b850v3_dp2_bridge.txt
> +
>  GENERIC GPIO I2C DRIVER
>  M:   Haavard Skinnemoen 
>  S:   Supported
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index b590e67..b4b70fb 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -32,6 +32,17 @@ config DRM_DW_HDMI_AHB_AUDIO
> Designware HDMI block.  This is used in conjunction with
> the i.MX6 HDMI driver.
>  
> +config DRM_GE_B850V3_LVDS_DP
> + tristate "GE B850v3 LVDS to DP++ display bridge"
> + depends on OF
> + select DRM_KMS_HELPER
> + select DRM_PANEL
> + ---help---
> +  This is a driver for the display bridge of
> +  GE B850v3 that convert dual channel LVDS
> +  to DP++. This is used with the i.MX6 imx-ldb
> +  driver.
> +
>  config DRM_NXP_PTN3460
>   tristate "NXP PTN3460 DP/LVDS bridge"
>   depends on OF
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index efdb07e..b9606f3 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -3,6 +3,7 @@ ccflags-y := -Iinclude/drm
>  obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
>  obj-$(CONFIG_DRM_DW_HDMI) += dw-hdmi.o
>  obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
> +obj-$(CONFIG_DRM_GE_B850V3_LVDS_DP) += ge_b850v3_lvds_dp.o
>  obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
>  obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
>  obj-$(CONFIG_DRM_SII902X) += sii902x.o
> diff --git a/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c 
> b/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
> new file mode 100644
> index 000..81e9279
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
> @@ -0,0 +1,405 @@
> +/*
> + * Driver for GE B850v3 DP display bridge
> +
> + * Copyright (c) 2016, Collabora Ltd.
> + * Copyright (c) 2016, General Electric Company
> +
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> +
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY 

[PATCH V5 3/4] drm/bridge: Add driver for GE B850v3 LVDS/DP++ Bridge

[Archit Taneja]

Hi,

On 08/09/2016 10:11 PM, Peter Senna Tschudin wrote:
> Add a driver that create a drm_bridge and a drm_connector for the LVDS
> to DP++ display bridge of the GE B850v3.
>
> There are two physical bridges on the video signal pipeline: a
> STDP4028(LVDS to DP) and a STDP2690(DP to DP++).  The hardware and
> firmware made it complicated for this binding to comprise two device
> tree nodes, as the design goal is to configure both bridges based on
> the LVDS signal, which leave the driver powerless to control the video
> processing pipeline. The two bridges behaves as a single bridge, and
> the driver is only needed for telling the host about EDID / HPD, and
> for giving the host powers to ack interrupts. The video signal pipeline
> is as follows:
>
>Host -> LVDS|--(STDP4028)--|DP -> DP|--(STDP2690)--|DP++ -> Video output
>

I'd commented on an earlier revision (v2) of this patch, but hadn't got
a response on it. Pasting the query again:

Are these two chips always expected to be used together? I don't think
it's right to pair up two encoder chips into one driver just for one
board.

Is one device @0x72 and other @0x73? Or is only one of them an i2c
slave?

What's preventing us to create these as two different bridge drivers?
The drm framework allows us to daisy chain encoder bridges. The only
problem I see is that we don't have a clear-cut way to tell the bridge
driver whether we want it to create a connector for us or not. Because,
it looks like both can potentially create connectors. This isn't a big
problem either if we have DT. We just need to check whether our output
port is connected to another bridge or a connector.

Thanks,
Archit

> Cc: Martyn Welch 
> Cc: Martin Donnelly 
> Cc: Daniel Vetter 
> Cc: Enric Balletbo i Serra 
> Cc: Philipp Zabel 
> Cc: Rob Herring 
> Cc: Fabio Estevam 
> CC: David Airlie 
> CC: Thierry Reding 
> CC: Thierry Reding 
> Reviewed-by: Enric Balletbo 
> Signed-off-by: Peter Senna Tschudin 
> ---
> Changes from V4:
>   - Check the output of the first call to i2c_smbus_write_word_data() and 
> return
> it's error code for failing gracefully on i2c issues
>   - Renamed the i2c_driver.name from "ge,b850v3-lvds-dp" to "b850v3-lvds-dp" 
> to
> remove the comma from the driver name
>
> Changes from V3:
>   - 3/4 instead of 4/5
>   - Tested on next-20160804
>
> Changes from V2:
>   - Made it atomic to be applied on next-20160729 on top of Liu Ying changes
> that made imx-ldb atomic
>
> Changes from V1:
>   - New commit message
>   - Removed 3 empty entry points
>   - Removed memory leak from ge_b850v3_lvds_dp_get_modes()
>   - Added a lock for mode setting
>   - Removed a few blank lines
>   - Changed the order at Makefile and Kconfig
>
>   MAINTAINERS|   8 +
>   drivers/gpu/drm/bridge/Kconfig |  11 +
>   drivers/gpu/drm/bridge/Makefile|   1 +
>   drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c | 405 
> +
>   4 files changed, 425 insertions(+)
>   create mode 100644 drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a306795..e8d106a 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5142,6 +5142,14 @@ W: https://linuxtv.org
>   S:  Maintained
>   F:  drivers/media/radio/radio-gemtek*
>
> +GENERAL ELECTRIC B850V3 LVDS/DP++ BRIDGE
> +M:   Peter Senna Tschudin 
> +M:   Martin Donnelly 
> +M:   Martyn Welch 
> +S:   Maintained
> +F:   drivers/gpu/drm/bridge/ge_b850v3_dp2.c
> +F:   Documentation/devicetree/bindings/ge/b850v3_dp2_bridge.txt
> +
>   GENERIC GPIO I2C DRIVER
>   M:  Haavard Skinnemoen 
>   S:  Supported
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index b590e67..b4b70fb 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -32,6 +32,17 @@ config DRM_DW_HDMI_AHB_AUDIO
> Designware HDMI block.  This is used in conjunction with
> the i.MX6 HDMI driver.
>
> +config DRM_GE_B850V3_LVDS_DP
> + tristate "GE B850v3 LVDS to DP++ display bridge"
> + depends on OF
> + select DRM_KMS_HELPER
> + select DRM_PANEL
> + ---help---
> +  This is a driver for the display bridge of
> +  GE B850v3 that convert dual channel LVDS
> +  to DP++. This is used with the i.MX6 imx-ldb
> +  driver.
> +
>   config DRM_NXP_PTN3460
>   tristate "NXP PTN3460 DP/LVDS bridge"
>   depends on OF
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index efdb07e..b9606f3 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -3,6 +3,7 @@ ccflags-y := -Iinclude/drm
>   obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
>   obj-$(CONFIG_DRM_DW_HDMI) += dw-hdmi.o
>   obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
> +obj-$(CONFIG_DRM_GE_B850V3_LVDS_DP) += ge_b850v3_lvds_dp.o
>   obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
>   

[PATCH V5 3/4] drm/bridge: Add driver for GE B850v3 LVDS/DP++ Bridge

[Peter Senna Tschudin]

Add a driver that create a drm_bridge and a drm_connector for the LVDS
to DP++ display bridge of the GE B850v3.

There are two physical bridges on the video signal pipeline: a
STDP4028(LVDS to DP) and a STDP2690(DP to DP++).  The hardware and
firmware made it complicated for this binding to comprise two device
tree nodes, as the design goal is to configure both bridges based on
the LVDS signal, which leave the driver powerless to control the video
processing pipeline. The two bridges behaves as a single bridge, and
the driver is only needed for telling the host about EDID / HPD, and
for giving the host powers to ack interrupts. The video signal pipeline
is as follows:

  Host -> LVDS|--(STDP4028)--|DP -> DP|--(STDP2690)--|DP++ -> Video output

Cc: Martyn Welch 
Cc: Martin Donnelly 
Cc: Daniel Vetter 
Cc: Enric Balletbo i Serra 
Cc: Philipp Zabel 
Cc: Rob Herring 
Cc: Fabio Estevam 
CC: David Airlie 
CC: Thierry Reding 
CC: Thierry Reding 
Reviewed-by: Enric Balletbo 
Signed-off-by: Peter Senna Tschudin 
---
Changes from V4:
 - Check the output of the first call to i2c_smbus_write_word_data() and return
   it's error code for failing gracefully on i2c issues
 - Renamed the i2c_driver.name from "ge,b850v3-lvds-dp" to "b850v3-lvds-dp" to
   remove the comma from the driver name

Changes from V3:
 - 3/4 instead of 4/5
 - Tested on next-20160804

Changes from V2:
 - Made it atomic to be applied on next-20160729 on top of Liu Ying changes
   that made imx-ldb atomic

Changes from V1:
 - New commit message
 - Removed 3 empty entry points
 - Removed memory leak from ge_b850v3_lvds_dp_get_modes()
 - Added a lock for mode setting
 - Removed a few blank lines
 - Changed the order at Makefile and Kconfig

 MAINTAINERS|   8 +
 drivers/gpu/drm/bridge/Kconfig |  11 +
 drivers/gpu/drm/bridge/Makefile|   1 +
 drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c | 405 +
 4 files changed, 425 insertions(+)
 create mode 100644 drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c

diff --git a/MAINTAINERS b/MAINTAINERS
index a306795..e8d106a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5142,6 +5142,14 @@ W:   https://linuxtv.org
 S: Maintained
 F: drivers/media/radio/radio-gemtek*

+GENERAL ELECTRIC B850V3 LVDS/DP++ BRIDGE
+M: Peter Senna Tschudin 
+M: Martin Donnelly 
+M: Martyn Welch 
+S: Maintained
+F: drivers/gpu/drm/bridge/ge_b850v3_dp2.c
+F: Documentation/devicetree/bindings/ge/b850v3_dp2_bridge.txt
+
 GENERIC GPIO I2C DRIVER
 M: Haavard Skinnemoen 
 S: Supported
diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index b590e67..b4b70fb 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -32,6 +32,17 @@ config DRM_DW_HDMI_AHB_AUDIO
  Designware HDMI block.  This is used in conjunction with
  the i.MX6 HDMI driver.

+config DRM_GE_B850V3_LVDS_DP
+   tristate "GE B850v3 LVDS to DP++ display bridge"
+   depends on OF
+   select DRM_KMS_HELPER
+   select DRM_PANEL
+   ---help---
+  This is a driver for the display bridge of
+  GE B850v3 that convert dual channel LVDS
+  to DP++. This is used with the i.MX6 imx-ldb
+  driver.
+
 config DRM_NXP_PTN3460
tristate "NXP PTN3460 DP/LVDS bridge"
depends on OF
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index efdb07e..b9606f3 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -3,6 +3,7 @@ ccflags-y := -Iinclude/drm
 obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
 obj-$(CONFIG_DRM_DW_HDMI) += dw-hdmi.o
 obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
+obj-$(CONFIG_DRM_GE_B850V3_LVDS_DP) += ge_b850v3_lvds_dp.o
 obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
 obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
 obj-$(CONFIG_DRM_SII902X) += sii902x.o
diff --git a/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c 
b/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
new file mode 100644
index 000..81e9279
--- /dev/null
+++ b/drivers/gpu/drm/bridge/ge_b850v3_lvds_dp.c
@@ -0,0 +1,405 @@
+/*
+ * Driver for GE B850v3 DP display bridge
+
+ * Copyright (c) 2016, Collabora Ltd.
+ * Copyright (c) 2016, General Electric Company
+
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see .
+
+ * This driver creates a drm_bridge and a