DRM Driver implementation question

Gareth Williams gareth.williams.jx at renesas.com
Tue Sep 17 15:27:34 UTC 2019

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

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