[PATCH 06/16] drm/omap: remove dma & vrfb rotation

[Tomi Valkeinen]

On 24/05/17 12:31, Laurent Pinchart wrote:
> Hi Tomi,
> 
> Thank you for the patch.
> 
> On Thursday 04 May 2017 13:23:22 Tomi Valkeinen wrote:
>> We have three rotation methods supported by the SoCs with DSS: DMA,
>> VRFB and TILER.
>>
>> DMA rotation works in theory on all DSS platforms, but in practice it's
>> unusable due to the huge amount of memory bandwidth it uses, and has
>> never really been used.
>>
>> VRFB is available on OMAP3, but is not supported by omapdrm, even though
>> we have some code for it in the dispc driver.
>>
>> TILER is supported on OMAP4/OMAP5/DRA7/AM5 platforms, but has some
>> driver bugs.
>>
>> To clean up the driver to help fixing the TILER issues, this patch drops
>> the DMA and VRFB rotation support, leaving only TILER rotation.
> 
> I'm fine dropping DMA rotation, but I have mixed feelings about VRFB. Yes, it 
> doesn't work at the moment, but I know users of VRFB with the omap_vout driver 
> who would really like to switch to omapdrm. Porting VRFB from omap_vout to 
> omapdrm has been on my to-do list for a long time (with a low priority 
> unfortunately). As an added bonus, it would allow dropping the omap_vout 
> driver at some point.
> 
> What would you think about dropping DMA but keeping VRFB for now ?

This patch doesn't remove that much about vrfb, just the row/pix inc
calculations. The main vrfb file is still there, for omapfb. I'm happy
to add it back when someone has a working prototype for omapdrm+vrfb,
but to be honest, I won't hold my breath =).

I really want to clean up the dispc driver as much as possible, as it's
such a messy piece of code, supporting so many DSS IP versions. I
believe we'll get a cleaner version if we add the vrfb back from scratch.

 Tomi

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