[Intel-gfx] [PATCH 2/6] drm/atomic: Unconditionally call prepare_fb.

[Maarten Lankhorst]

Op 09-12-16 om 09:25 schreef Daniel Vetter:
> On Fri, Dec 09, 2016 at 12:42:19AM +0200, Laurent Pinchart wrote:
>> Hi Daniel,
>>
>> On Thursday 08 Dec 2016 16:41:04 Daniel Vetter wrote:
>>> On Thu, Dec 08, 2016 at 02:45:25PM +0100, Maarten Lankhorst wrote:
>>>> Atomic drivers may set properties like rotation on the same fb, which
>>>> may require a call to prepare_fb even when framebuffer stays identical.
>>>>
>>>> Instead of handling all the special cases in the core, let the driver
>>>> decide when prepare_fb and cleanup_fb are noops.
>>>>
>>>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
>>> I think this makes sense, but would be really good to get a pile of acks
>>> from driver maintainers on this one. Rob, Eric, Laurent, others?
>> This is all very nice, but it will introduce at least a performance 
>> regression, and possibly worse, until drivers get updated. There are 7 drivers 
>> implementing the .prepare_fb() callback (plus a bunch of drivers that probably 
>> should use drm_fb_cma_prepare_fb() but don't at the moment). I can't ack this 
>> patch before they get fixed.
> Maarten's commit message is insufficient, since this is defacto a revert
> of
>
> commit fcc60b413d14dd06ddbd79ec50e83c4fb2a097ba
> Author: Keith Packard <keithp at keithp.com>
> Date:   Sat Jun 4 01:16:22 2016 -0700
>
>     drm: Don't prepare or cleanup unchanging frame buffers [v3]
>
> because that breaks stuff. We're simply going back to where we've been a
> few months ago. Since this is a regression fix, back to original
> behaviour, can you ack (assuming Maarten updates the commit message to
> reflect the nature of the commit here)?

Waiting on a reply, but what about this commit message for this patch?
---
Atomic drivers may set properties like rotation on the same fb, which
may require a call to prepare_fb even when framebuffer stays identical.

Instead of handling all the special cases in the core, let the driver
decide when prepare_fb and cleanup_fb are noops.

This is a revert of:

commit fcc60b413d14dd06ddbd79ec50e83c4fb2a097ba
Author: Keith Packard <keithp at keithp.com>
Date:   Sat Jun 4 01:16:22 2016 -0700

    drm: Don't prepare or cleanup unchanging frame buffers [v3]

The original commit mentions that this prevents waiting in i915 on all
previous rendering during cursor updates, but there are better ways to
fix this.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>