Re: [PATCH] phy: rcar-gen3-usb2: add sysfs for usb role swap

[Geert Uytterhoeven]

Hi Shimoda-san,

On Tue, Oct 18, 2016 at 8:19 AM, Yoshihiro Shimoda
 wrote:
>> From: geert.uytterhoe...@gmail.com
>> Sent: Monday, October 17, 2016 9:28 PM
>> On Mon, Oct 17, 2016 at 9:10 AM, Yoshihiro Shimoda
>>  wrote:
>> > This patch adds sysfs "otg_inputs" for usb role swap. This parameter
>> > is write-only and if you use them as the following, you can swap
>> > the usb role.
>>
>> Thank you for your patch!
>
> Thank you for the review!
>
>> > For example:
>> >  1) connect a usb cable using 2 salvator-x boards
>> >  2) On A-device (as host), you input the following command:
>> ># echo a_bus_req/ > 
>> > /sys/devices/platform/soc/ee080200.usb-phy/otg_inputs
>> >  3) On B-device (as peripheral), you input the following command:
>> ># echo b_bus_req > /sys/devices/platform/soc/ee080200.usb-phy/otg_inputs
>>
>> At first, I thought the trailing "/" was a typo...
>>
>> > --- /dev/null
>> > +++ b/Documentation/ABI/testing/sysfs-platform-phy-rcar-gen3-usb2
>> > @@ -0,0 +1,11 @@
>> > +What:  /sys/devices/platform//otg-inputs
>> > +Date:  October 2016
>> > +KernelVersion: 4.10
>> > +Contact:   Yoshihiro Shimoda 
>> > +Description:
>> > +   This write-only file changes the phy mode for role swap of 
>> > usb.
>> > +   This file accepts the following strings:
>> > +"a_bus_req/" - switching from A-Host to A-Peripheral
>> > +"a_bus_drop" - switching from A-Peripheral to A-Host
>> > +"b_bus_req"  - switching from B-Peripheral to B-Host
>> > +"b_bus_req/" - switching from B-Host to B-Peripheral
>>
>> ... until I read the above.
>>
>> What's the rationale of doing it like this? I.e.
>>   1. Why differentiate by trailing "/"?
>
> This usb role swap feature is not compatible with USB OTG though,
> but this strings are from the manual that usb.org released:
> http://www.usb.org/developers/docs/usb20_docs/
>  --> usb_20_091216.zip
>   --> USB OTG and Embedded Host/USB_OTG_and_EH_2-0-version 1_1a.pdf
>Please refer to the following figures:
> - Figure 7-1: OTG A-device with HNP State Diagram
> - Figure 7-4: OTG B-device with HNP State Diagram
>
> So, it seems the "/" means FALSE.
>
>>   2. Why the asymmetry ("a_bus_drop" vs. "a_bus_req")?
>
> This is also related the document.
>  - From "a_host" to "a_suspend" state if "a_bus_req/" event happens.
>  - From "a_suspend" to "a_host" state if "a_bus_req" event happens.
>   (But the driver doesn't support it and we can use "a_bus_drop".)
>  - From "a_peripheral" to "a_wait_vfall" state if "a_bus_drop" event happens.

Thanks for the explanation!

Regardless, I think it would be good to CC the USB maintainer and mailing
list on next submission.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

Re: [PATCH] phy: rcar-gen3-usb2: add sysfs for usb role swap

[Geert Uytterhoeven]

Hi Shimoda-san,

On Tue, Oct 18, 2016 at 8:19 AM, Yoshihiro Shimoda
 wrote:
>> From: geert.uytterhoe...@gmail.com
>> Sent: Monday, October 17, 2016 9:28 PM
>> On Mon, Oct 17, 2016 at 9:10 AM, Yoshihiro Shimoda
>>  wrote:
>> > This patch adds sysfs "otg_inputs" for usb role swap. This parameter
>> > is write-only and if you use them as the following, you can swap
>> > the usb role.
>>
>> Thank you for your patch!
>
> Thank you for the review!
>
>> > For example:
>> >  1) connect a usb cable using 2 salvator-x boards
>> >  2) On A-device (as host), you input the following command:
>> ># echo a_bus_req/ > 
>> > /sys/devices/platform/soc/ee080200.usb-phy/otg_inputs
>> >  3) On B-device (as peripheral), you input the following command:
>> ># echo b_bus_req > /sys/devices/platform/soc/ee080200.usb-phy/otg_inputs
>>
>> At first, I thought the trailing "/" was a typo...
>>
>> > --- /dev/null
>> > +++ b/Documentation/ABI/testing/sysfs-platform-phy-rcar-gen3-usb2
>> > @@ -0,0 +1,11 @@
>> > +What:  /sys/devices/platform//otg-inputs
>> > +Date:  October 2016
>> > +KernelVersion: 4.10
>> > +Contact:   Yoshihiro Shimoda 
>> > +Description:
>> > +   This write-only file changes the phy mode for role swap of 
>> > usb.
>> > +   This file accepts the following strings:
>> > +"a_bus_req/" - switching from A-Host to A-Peripheral
>> > +"a_bus_drop" - switching from A-Peripheral to A-Host
>> > +"b_bus_req"  - switching from B-Peripheral to B-Host
>> > +"b_bus_req/" - switching from B-Host to B-Peripheral
>>
>> ... until I read the above.
>>
>> What's the rationale of doing it like this? I.e.
>>   1. Why differentiate by trailing "/"?
>
> This usb role swap feature is not compatible with USB OTG though,
> but this strings are from the manual that usb.org released:
> http://www.usb.org/developers/docs/usb20_docs/
>  --> usb_20_091216.zip
>   --> USB OTG and Embedded Host/USB_OTG_and_EH_2-0-version 1_1a.pdf
>Please refer to the following figures:
> - Figure 7-1: OTG A-device with HNP State Diagram
> - Figure 7-4: OTG B-device with HNP State Diagram
>
> So, it seems the "/" means FALSE.
>
>>   2. Why the asymmetry ("a_bus_drop" vs. "a_bus_req")?
>
> This is also related the document.
>  - From "a_host" to "a_suspend" state if "a_bus_req/" event happens.
>  - From "a_suspend" to "a_host" state if "a_bus_req" event happens.
>   (But the driver doesn't support it and we can use "a_bus_drop".)
>  - From "a_peripheral" to "a_wait_vfall" state if "a_bus_drop" event happens.

Thanks for the explanation!

Regardless, I think it would be good to CC the USB maintainer and mailing
list on next submission.

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

RE: [PATCH] phy: rcar-gen3-usb2: add sysfs for usb role swap

[Yoshihiro Shimoda]

Hi Geert-san,

> From: geert.uytterhoe...@gmail.com
> Sent: Monday, October 17, 2016 9:28 PM
> 
> Hi Shimoda-san,
> 
> On Mon, Oct 17, 2016 at 9:10 AM, Yoshihiro Shimoda
>  wrote:
> > This patch adds sysfs "otg_inputs" for usb role swap. This parameter
> > is write-only and if you use them as the following, you can swap
> > the usb role.
> 
> Thank you for your patch!

Thank you for the review!

> > For example:
> >  1) connect a usb cable using 2 salvator-x boards
> >  2) On A-device (as host), you input the following command:
> ># echo a_bus_req/ > /sys/devices/platform/soc/ee080200.usb-phy/otg_inputs
> >  3) On B-device (as peripheral), you input the following command:
> ># echo b_bus_req > /sys/devices/platform/soc/ee080200.usb-phy/otg_inputs
> 
> At first, I thought the trailing "/" was a typo...
> 
> > --- /dev/null
> > +++ b/Documentation/ABI/testing/sysfs-platform-phy-rcar-gen3-usb2
> > @@ -0,0 +1,11 @@
> > +What:  /sys/devices/platform//otg-inputs
> > +Date:  October 2016
> > +KernelVersion: 4.10
> > +Contact:   Yoshihiro Shimoda 
> > +Description:
> > +   This write-only file changes the phy mode for role swap of 
> > usb.
> > +   This file accepts the following strings:
> > +"a_bus_req/" - switching from A-Host to A-Peripheral
> > +"a_bus_drop" - switching from A-Peripheral to A-Host
> > +"b_bus_req"  - switching from B-Peripheral to B-Host
> > +"b_bus_req/" - switching from B-Host to B-Peripheral
> 
> ... until I read the above.
> 
> What's the rationale of doing it like this? I.e.
>   1. Why differentiate by trailing "/"?

This usb role swap feature is not compatible with USB OTG though,
but this strings are from the manual that usb.org released:
http://www.usb.org/developers/docs/usb20_docs/
 --> usb_20_091216.zip
  --> USB OTG and Embedded Host/USB_OTG_and_EH_2-0-version 1_1a.pdf
   Please refer to the following figures:
- Figure 7-1: OTG A-device with HNP State Diagram
- Figure 7-4: OTG B-device with HNP State Diagram

So, it seems the "/" means FALSE.

>   2. Why the asymmetry ("a_bus_drop" vs. "a_bus_req")?

This is also related the document.
 - From "a_host" to "a_suspend" state if "a_bus_req/" event happens.
 - From "a_suspend" to "a_host" state if "a_bus_req" event happens.
  (But the driver doesn't support it and we can use "a_bus_drop".)
 - From "a_peripheral" to "a_wait_vfall" state if "a_bus_drop" event happens.

> I do not really follow USB development, so I please accepty my apologies if
> I missed the discussion and valid arguments that lead to this.
> 
> I did find Documentation/ABI/testing/sysfs-platform-chipidea-usb-otg,
> which uses similar naming, but a slightly different mechanism (multiple
> sysfs virtual files with 0/1 states).

I also did look at the document. But, I prefer one parameter to control it.

Best regards,
Yoshihiro Shimoda

> Thanks!
> 
> Gr{oetje,eeting}s,
> 
> Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- 
> ge...@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like 
> that.
> -- Linus Torvalds

RE: [PATCH] phy: rcar-gen3-usb2: add sysfs for usb role swap

[Yoshihiro Shimoda]

Hi Geert-san,

> From: geert.uytterhoe...@gmail.com
> Sent: Monday, October 17, 2016 9:28 PM
> 
> Hi Shimoda-san,
> 
> On Mon, Oct 17, 2016 at 9:10 AM, Yoshihiro Shimoda
>  wrote:
> > This patch adds sysfs "otg_inputs" for usb role swap. This parameter
> > is write-only and if you use them as the following, you can swap
> > the usb role.
> 
> Thank you for your patch!

Thank you for the review!

> > For example:
> >  1) connect a usb cable using 2 salvator-x boards
> >  2) On A-device (as host), you input the following command:
> ># echo a_bus_req/ > /sys/devices/platform/soc/ee080200.usb-phy/otg_inputs
> >  3) On B-device (as peripheral), you input the following command:
> ># echo b_bus_req > /sys/devices/platform/soc/ee080200.usb-phy/otg_inputs
> 
> At first, I thought the trailing "/" was a typo...
> 
> > --- /dev/null
> > +++ b/Documentation/ABI/testing/sysfs-platform-phy-rcar-gen3-usb2
> > @@ -0,0 +1,11 @@
> > +What:  /sys/devices/platform//otg-inputs
> > +Date:  October 2016
> > +KernelVersion: 4.10
> > +Contact:   Yoshihiro Shimoda 
> > +Description:
> > +   This write-only file changes the phy mode for role swap of 
> > usb.
> > +   This file accepts the following strings:
> > +"a_bus_req/" - switching from A-Host to A-Peripheral
> > +"a_bus_drop" - switching from A-Peripheral to A-Host
> > +"b_bus_req"  - switching from B-Peripheral to B-Host
> > +"b_bus_req/" - switching from B-Host to B-Peripheral
> 
> ... until I read the above.
> 
> What's the rationale of doing it like this? I.e.
>   1. Why differentiate by trailing "/"?

This usb role swap feature is not compatible with USB OTG though,
but this strings are from the manual that usb.org released:
http://www.usb.org/developers/docs/usb20_docs/
 --> usb_20_091216.zip
  --> USB OTG and Embedded Host/USB_OTG_and_EH_2-0-version 1_1a.pdf
   Please refer to the following figures:
- Figure 7-1: OTG A-device with HNP State Diagram
- Figure 7-4: OTG B-device with HNP State Diagram

So, it seems the "/" means FALSE.

>   2. Why the asymmetry ("a_bus_drop" vs. "a_bus_req")?

This is also related the document.
 - From "a_host" to "a_suspend" state if "a_bus_req/" event happens.
 - From "a_suspend" to "a_host" state if "a_bus_req" event happens.
  (But the driver doesn't support it and we can use "a_bus_drop".)
 - From "a_peripheral" to "a_wait_vfall" state if "a_bus_drop" event happens.

> I do not really follow USB development, so I please accepty my apologies if
> I missed the discussion and valid arguments that lead to this.
> 
> I did find Documentation/ABI/testing/sysfs-platform-chipidea-usb-otg,
> which uses similar naming, but a slightly different mechanism (multiple
> sysfs virtual files with 0/1 states).

I also did look at the document. But, I prefer one parameter to control it.

Best regards,
Yoshihiro Shimoda

> Thanks!
> 
> Gr{oetje,eeting}s,
> 
> Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- 
> ge...@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like 
> that.
> -- Linus Torvalds

Re: [PATCH] phy: rcar-gen3-usb2: add sysfs for usb role swap

[Geert Uytterhoeven]

Hi Shimoda-san,

On Mon, Oct 17, 2016 at 9:10 AM, Yoshihiro Shimoda
 wrote:
> This patch adds sysfs "otg_inputs" for usb role swap. This parameter
> is write-only and if you use them as the following, you can swap
> the usb role.

Thank you for your patch!

> For example:
>  1) connect a usb cable using 2 salvator-x boards
>  2) On A-device (as host), you input the following command:
># echo a_bus_req/ > /sys/devices/platform/soc/ee080200.usb-phy/otg_inputs
>  3) On B-device (as peripheral), you input the following command:
># echo b_bus_req > /sys/devices/platform/soc/ee080200.usb-phy/otg_inputs

At first, I thought the trailing "/" was a typo...

> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-platform-phy-rcar-gen3-usb2
> @@ -0,0 +1,11 @@
> +What:  /sys/devices/platform//otg-inputs
> +Date:  October 2016
> +KernelVersion: 4.10
> +Contact:   Yoshihiro Shimoda 
> +Description:
> +   This write-only file changes the phy mode for role swap of 
> usb.
> +   This file accepts the following strings:
> +"a_bus_req/" - switching from A-Host to A-Peripheral
> +"a_bus_drop" - switching from A-Peripheral to A-Host
> +"b_bus_req"  - switching from B-Peripheral to B-Host
> +"b_bus_req/" - switching from B-Host to B-Peripheral

... until I read the above.

What's the rationale of doing it like this? I.e.
  1. Why differentiate by trailing "/"?
  2. Why the asymmetry ("a_bus_drop" vs. "a_bus_req")?

I do not really follow USB development, so I please accepty my apologies if
I missed the discussion and valid arguments that lead to this.

I did find Documentation/ABI/testing/sysfs-platform-chipidea-usb-otg,
which uses similar naming, but a slightly different mechanism (multiple
sysfs virtual files with 0/1 states).

Thanks!

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

Re: [PATCH] phy: rcar-gen3-usb2: add sysfs for usb role swap

[Geert Uytterhoeven]

Hi Shimoda-san,

On Mon, Oct 17, 2016 at 9:10 AM, Yoshihiro Shimoda
 wrote:
> This patch adds sysfs "otg_inputs" for usb role swap. This parameter
> is write-only and if you use them as the following, you can swap
> the usb role.

Thank you for your patch!

> For example:
>  1) connect a usb cable using 2 salvator-x boards
>  2) On A-device (as host), you input the following command:
># echo a_bus_req/ > /sys/devices/platform/soc/ee080200.usb-phy/otg_inputs
>  3) On B-device (as peripheral), you input the following command:
># echo b_bus_req > /sys/devices/platform/soc/ee080200.usb-phy/otg_inputs

At first, I thought the trailing "/" was a typo...

> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-platform-phy-rcar-gen3-usb2
> @@ -0,0 +1,11 @@
> +What:  /sys/devices/platform//otg-inputs
> +Date:  October 2016
> +KernelVersion: 4.10
> +Contact:   Yoshihiro Shimoda 
> +Description:
> +   This write-only file changes the phy mode for role swap of 
> usb.
> +   This file accepts the following strings:
> +"a_bus_req/" - switching from A-Host to A-Peripheral
> +"a_bus_drop" - switching from A-Peripheral to A-Host
> +"b_bus_req"  - switching from B-Peripheral to B-Host
> +"b_bus_req/" - switching from B-Host to B-Peripheral

... until I read the above.

What's the rationale of doing it like this? I.e.
  1. Why differentiate by trailing "/"?
  2. Why the asymmetry ("a_bus_drop" vs. "a_bus_req")?

I do not really follow USB development, so I please accepty my apologies if
I missed the discussion and valid arguments that lead to this.

I did find Documentation/ABI/testing/sysfs-platform-chipidea-usb-otg,
which uses similar naming, but a slightly different mechanism (multiple
sysfs virtual files with 0/1 states).

Thanks!

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds