[Intel-gfx] [RFC PATCH 11/18] drm/i915: Updating the crtc modes in DRRS transitions

[Daniel Vetter]

On Mon, Jun 29, 2015 at 08:28:53PM +0530, Ramalingam C wrote:
> 
> On Friday 26 June 2015 10:41 PM, Daniel Vetter wrote:
> >On Fri, Jun 26, 2015 at 07:21:55PM +0530, Ramalingam C wrote:
> >>During the DRRS state transitions we are modifying the clock and
> >>hence the vrefresh rate.
> >>
> >>So we need to update the drm_crtc->mode and the adjusted
> >>mode in intel_crtc. So that watermark calculations will be as per the
> >>new modified clock.
> >>
> >>Signed-off-by: Ramalingam C<ramalingam.c at intel.com>
> >>---
> >>  drivers/gpu/drm/i915/intel_drrs.c     |   14 ++++++++++++++
> >>  drivers/gpu/drm/i915/intel_dsi_drrs.c |   14 +++++++++++++-
> >>  2 files changed, 27 insertions(+), 1 deletion(-)
> >>
> >>diff --git a/drivers/gpu/drm/i915/intel_drrs.c b/drivers/gpu/drm/i915/intel_drrs.c
> >>index 42b420d..2901832 100644
> >>--- a/drivers/gpu/drm/i915/intel_drrs.c
> >>+++ b/drivers/gpu/drm/i915/intel_drrs.c
> >>@@ -169,6 +169,20 @@ void intel_set_drrs_state(struct i915_drrs *drrs)
> >>  		 * If it is non-DSI encoders.
> >>  		 * As only DSI has SEAMLESS_DRRS_SUPPORT_SW.
> >>  		 */
> >>+		/*
> >>+		 * TODO: Protect the access to the crtc mode with corresponding
> >>+		 * mutex in case of Idleness DRRS. As media playback update
> >>+		 * will happen under crtc modeset lock protection
> >>+		 */
> >>+		drm_modeset_lock(&intel_crtc->base.mutex, NULL);
> >>+		intel_crtc->base.mode.clock = target_mode->clock;
> >>+		intel_crtc->base.mode.vrefresh = target_mode->vrefresh;
> >>+		intel_crtc->config->base.adjusted_mode.clock =
> >>+							target_mode->clock;
> >>+		intel_crtc->config->base.adjusted_mode.vrefresh =
> >>+							target_mode->vrefresh;
> >>+		drm_modeset_unlock(&intel_crtc->base.mutex);
> >No. For video DRRS (i.e. changing the vrefresh rate to exactly what we
> >want to match media content) userspace needs to do a full modeset. Maarten
> >is working on infrastructure to avoid full modeset in some special mode
> >changes (to implement the fast pfit change from Jesse's original fastboot
> >work). And we can extend this to DRRS too.
> Daniel,
> 
> But this interface that we have developed for android is not just for video
> playback.
> We are trying to provide a interface where user space can request for custom
> vrefresh,
> if the rate of the display content doesn't need the vrefresh of current
> applied mode.

Well I just called it video DRRS since I thought that's the main use-case.
The interface I'm proposing here (which already exists, that's the point)
will of course work no matter what exactly you're displaying.

> For example scenarios like text editor or some game where lower Frame per
> second is sufficient. And if the panel supports
> the seamless drrs we don't need to do a modeset in such scenarios.
> 
> Either way Please do share/point to the details of the Maarten design. So
> that we can see if we are
> working on same area and if so how far we can reuse each others work.

Maarten is still debugging a pile of fallout in unrelated code, probably
best if you ping him directly on irc about the latest stuff.

> >For seamless&transparent DRRS we can still keep the current design with
> >effectively 2 dotclocks.
> You mean 2 dotclocks at drm_display_mode or drrs structure?

In intel_crtc_config we have two sets of DP m/n values, which means 2
different clocks for the sink. We also have pipe_config->port_clock. Just
need to extend that to low_port_clock for seamless DRRS (i.e. managed by
the kernel).
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch