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