Re: [PATCH 0/4] video: ARM CLCD: add support of an optional GPIO to enable panel

From: Vladimir Murzin <vladimir.murzin@arm.com>
To: linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 0/4] video: ARM CLCD: add support of an optional GPIO to enable panel
Date: Tue, 10 Jan 2017 13:47:01 +0000	[thread overview]
Message-ID: <50499352-fa14-64c4-1a74-db4827757a2d@arm.com> (raw)
In-Reply-To: <252ad888-fa9d-695a-58ed-46806e4374fd@mleia.com>

Hi Vladimir,

On 07/01/17 23:32, Vladimir Zapolskiy wrote:
> On 01/02/2017 04:22 PM, Russell King - ARM Linux wrote:
>> On Fri, Dec 30, 2016 at 09:23:59AM +0100, Linus Walleij wrote:
>>> On Wed, Dec 21, 2016 at 4:27 AM, Vladimir Zapolskiy <vz@mleia.com> wrote:
>>>
>>>> The changeset contains a number of cleanups, changed semantics of
>>>> init_panel() callback, which allows to simplify getting of panel
>>>> properties from panel device tree node, and a handling of optional
>>>> "enable-gpios" panel property, the latter is described in
>>>> display/panel/panel-dpi.txt device tree binding documentation, but
>>>> it has been unsupported by the ARM CLCD driver.
>>>>
>>>> Vladimir Zapolskiy (4):
>>>>   video: ARM CLCD: sort included headers out alphabetically
>>>>   video: ARM CLCD: use panel device node for panel initialization
>>>>   video: ARM CLCD: use panel device node for getting backlight and mode
>>>>   video: ARM CLCD: add support of an optional GPIO to enable panel
>>>
>>> As you may have seen Tomi has stepped down as FBDEV maintainer and
>>> this subsystem is now orphaned.
>>>
>>> I guess Andrew Morton merges patches for it in this case, he usually does.
>>>
>>> But what we should actually do is create a new DRM driver for CLCD
>>> in drivers/gpu/drm/arm/clcd*
>>>
>>> It's maybe not a small undertaking :(
>>>
>>> But in case you're interested in the job, I will pitch in and test the result
>>> on all ARM reference designs plus Nomadik.
>>
>> A DRM driver for it would probably be a good idea, but dealing with all
>> the weird and wonderful connection arrangements may not be that easy...
>>
> 
> Linus, Russell,
> 
> I've immediately encountered a problem while porting the driver to DRM,
> because LPC18xx/LPC43xx SoCs are powered by Cortex-M3/M4 cores and DRM
> framework has build and runtime dependencies on MMU.

+Benjamin

In another thread Benjamin pointed at patch [1] in drm/kms part for noMMU.

[1] https://cgit.freedesktop.org/drm/drm-misc/commit/?idba0d98a188cc4ebd8ea54b37d274ec20465e464

Cheers
Vladimir

> 
> That said, in short term I would expect a continuation of support for
> the legacy CLCD framebuffer driver, which works fine on MMU-less SoCs.
> 
> --
> With best wishes,
> Vladimir
> 
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