On Friday 04 April 2014 02:54 AM, Daniel Vetter wrote:
On Thu, Apr 03, 2014 at 02:28:32PM +0530, Archit Taneja wrote:
On Wednesday 02 April 2014 06:41 PM, Rob Clark wrote:
On Wed, Apr 2, 2014 at 5:52 AM, Archit Taneja <archit@xxxxxx> wrote:
Hi,
I was trying to figure out how we are supposed to manage synchronization
between a mode_set and a page_flip called on a crtc.
Say, if a mode_set is immediately followed by a page_flip. The driver can't
process the page_flip straight away since the hardware is still completing
the mode_set.
I guess setcrtc is expected to be synchronous(ish).. so a lot of
userspace won't expect the first pageflip to fail with -EBUSY.
Okay, thanks. I guess having setcrtc synchronous isn't that bad.
Yeah, atm I think the rules are that pageflip can only return -EBUSY if
there's still a pageflip ongoing. Everything else is presumed to be at
least implicitly ordered, so if your hw can do async modesets then you
need to synchronize. Also if there's still a pageflip outstanding you need
to wait for that to complete in your set_config callback first (usually in
the set_base or the crtc->disable/prepare hooks when using the crtc
helpers).
Thanks for the info. I didn't realize that the prepare/commit hooks get
executed when using drm_crtc_helper_set_mode() for the set_config helper.
Rob,
We disable the crtc in prepare, and enable it in commit.
If setcrtc changes the mode, I don't see how apply worker can execute
prepare() -> mode_set() -> commit() hooks in a row for the crtc
drm_crtc_helper_set_mode(). We can't queue more than one 'apply' of the
same entity. So the latter queues are bound to get rejected, I see
omap_crtc_apply() bailing out for crtc's apply in this case.
I guess making prepare() and mode_set() wait for a vsync should fix
this. Or, combining mode_set and commit as a single queue to apply
should work too. Any suggestions?
Thanks,
Archit
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