Re: [PATCH v5] drm/pl111: Initial drm/kms driver for pl111

[Eric Anholt <eric@anholt.net>]

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Linus Walleij <linus.walleij@linaro.org> writes:

> On Tue, Apr 11, 2017 at 3:18 AM, Eric Anholt <eric@anholt.net> wrote:
>
>> From: Tom Cooksey <tom.cooksey@arm.com>
>
> Well that can be debated at this point. I think it should have
> your Author: tag and just Tom in the Signed-off-by, then mention
> the history in the commit message.
>
>> This is a modesetting driver for the pl111 CLCD display controller
>> found on various ARM platforms such as the Versatile Express. The
>> driver has only been tested on the bcm911360_entphn platform so far,
>> with PRIME-based buffer sharing between vc4 and clcd.
>>
>> It reuses the existing devicetree binding, while not using quite as
>> many of its properties as the fbdev driver does (those are left for
>> future work).
>>
>> v2: Nearly complete rewrite by anholt, cutting 2/3 of the code thanks
>>     to DRM core's excellent new helpers.
>> v3: Don't match pl110 any more, don't attach if we don't have a DRM
>>     panel, use DRM_GEM_CMA_FOPS, update MAINTAINERS, use the simple
>>     display helper, use drm_gem_cma_dumb_create (same as our wrapper).
>> v4: Change the driver's .name to not clash with fbdev in sysfs, drop
>>     platform alias, drop redundant "drm" in DRM driver name, hook up
>>     .prepare_fb to the CMA helper so that DMA fences should work.
>> v5: Move register definitions inside the driver directory, fix build
>>     in COMPILE_TEST and !AMBA mode.
>>
>> Signed-off-by: Tom Cooksey <tom.cooksey@arm.com>
>> Signed-off-by: Eric Anholt <eric@anholt.net>
>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
>
> This is as good starting point as any. We need to get moving with
> this. Some minor things below that can just as well be fixed later.

Oh, one last thing I think we need to figure out: I'm using TIM2_CLKSEL,
which seems to be necessary on this platform.  My understanding is that
this means that the pixel clock is divided from clcdclk instead of
apb_pclk.  Do you agree?  The fbdev driver is using
clk_get(&fb->dev->dev, NULL) and not TIM2_CLKSEL, which I'm surprised by
because I would have thought that would give us the first clock from the
DT node (also clcdclk).

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