RE: DRM Driver implementation question
Hi Laurent, On Wed, Sep 18, 2019 at 04:04:34PM +, Laurent Pinchart wrote: > > Hi Gareth, > > Sorry for the delayed response, I was travelling for the Linux > Plumbers Conference followed by a code camp. > > On Tue, Sep 17, 2019 at 03:27:34PM +, Gareth Williams wrote: > > Hi Yoshihiro, > > > > This looks like an elegant solution that I can implement. > > Many thanks for pointing me in a good direction. > > > > > From: Yoshihiro Shimoda, Sent: Tuesday, September 17, 2019 05:39 > > > PM > > > > > > Hi Gareth, > > > > > > > From: Gareth Williams, Sent: Monday, September 16, 2019 10:56 PM > > > > > > > > Hi Laurent/Kieran, > > > > > > > > I need to upstream a driver for a display controller that within > > > > its registers memory region contains registers related to a PWM > > > > device. The PWM device is for controlling the backlight of the > > > > display. > > > > > > > > Ideally, I would like to create a separated driver for the PWM, > > > > so that I can re-use "pwm-backlight", but since the registers > > > > for the PWM are right in the middle of the registers for the > > > > display controller I would need to ioremap the memory region for > > > > the PWM registers region twice, once from the display controller > > > > driver, and once from the PWM driver. > > > > > > > > Do you think that the double ioremap would be acceptable upstream? > > > > > > I think that an MFD driver can support such hardware. I checked > > > Documentation/devicetree/bindings/mfd roughly, and then > > > atmel-hlcdc.txt seems to have a display controller and a PWM device. > > While MFD should technically work, I think it's quite overkill. You > could instead bundle both the display controller and the PWM > controller in the same driver. The driver would create both a DRM/KMS > device and a PWM device. The DT node for your device would contain a > #pwm-cells property and could thus be referenced as a PWM controller > by the backlight using the pwms property. This makes sense, many thanks for pointing me in the direction. > > -- > Regards, > > Laurent Pinchart Kind Regards, Gareth Williams
Re: DRM Driver implementation question
Hi Gareth, Sorry for the delayed response, I was travelling for the Linux Plumbers Conference followed by a code camp. On Tue, Sep 17, 2019 at 03:27:34PM +, Gareth Williams wrote: > Hi Yoshihiro, > > This looks like an elegant solution that I can implement. > Many thanks for pointing me in a good direction. > > > From: Yoshihiro Shimoda, Sent: Tuesday, September 17, 2019 05:39 PM > > > > Hi Gareth, > > > > > From: Gareth Williams, Sent: Monday, September 16, 2019 10:56 PM > > > > > > Hi Laurent/Kieran, > > > > > > I need to upstream a driver for a display controller that within its > > > registers memory region contains registers related to a PWM > > > device. The PWM device is for controlling the backlight of the > > > display. > > > > > > Ideally, I would like to create a separated driver for the PWM, so > > > that I can re-use "pwm-backlight", but since the registers for the PWM > > > are right in the middle of the registers for the display > > > controller I would need to ioremap the memory region for the PWM > > > registers region twice, once from the display controller driver, > > > and once from the PWM driver. > > > > > > Do you think that the double ioremap would be acceptable upstream? > > > > I think that an MFD driver can support such hardware. I checked > > Documentation/devicetree/bindings/mfd roughly, and then atmel-hlcdc.txt > > seems to have a display controller and a PWM device. While MFD should technically work, I think it's quite overkill. You could instead bundle both the display controller and the PWM controller in the same driver. The driver would create both a DRM/KMS device and a PWM device. The DT node for your device would contain a #pwm-cells property and could thus be referenced as a PWM controller by the backlight using the pwms property. -- Regards, Laurent Pinchart ___ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
RE: DRM Driver implementation question
Hi Yoshihiro, This looks like an elegant solution that I can implement. Many thanks for pointing me in a good direction. > From: Yoshihiro Shimoda, Sent: Tuesday, September 17, 2019 05:39 PM > > Hi Gareth, > > > From: Gareth Williams, Sent: Monday, September 16, 2019 10:56 PM > > > > Hi Laurent/Kieran, > > > > I need to upstream a driver for a display controller that within its > > registers memory region contains registers related to a PWM device. The > PWM device is for controlling the backlight of the display. > > Ideally, I would like to create a separated driver for the PWM, so > > that I can re-use "pwm-backlight", but since the registers for the PWM > > are right in the middle of the registers for the display controller I would > need to ioremap the memory region for the PWM registers region twice, > once from the display controller driver, and once from the PWM driver. > > Do you think that the double ioremap would be acceptable upstream? > > I think that an MFD driver can support such hardware. I checked > Documentation/devicetree/bindings/mfd roughly, and then atmel-hlcdc.txt > seems to have a display controller and a PWM device. > > Best regards, > Yoshihiro Shimoda Best Regards, Gareth Williams
RE: DRM Driver implementation question
Hi Gareth, > From: Gareth Williams, Sent: Monday, September 16, 2019 10:56 PM > > Hi Laurent/Kieran, > > I need to upstream a driver for a display controller that within its > registers memory region contains registers related > to a PWM device. The PWM device is for controlling the backlight of the > display. > Ideally, I would like to create a separated driver for the PWM, so that I can > re-use "pwm-backlight", but since the registers > for the PWM are right in the middle of the registers for the display > controller I would need to ioremap the memory region > for the PWM registers region twice, once from the display controller driver, > and once from the PWM driver. > Do you think that the double ioremap would be acceptable upstream? I think that an MFD driver can support such hardware. I checked Documentation/devicetree/bindings/mfd roughly, and then atmel-hlcdc.txt seems to have a display controller and a PWM device. Best regards, Yoshihiro Shimoda
