Re: [Intel-gfx] [PATCH v4 0/6] Finally fix watermarks

From: Matt Roper <matthew.d.roper@intel.com>
To: Lyude <cpaul@redhat.com>
Cc: intel-gfx@lists.freedesktop.org,
	"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
	"Ville Syrjälä" <ville.syrjala@linux.intel.com>,
	"David Airlie" <airlied@linux.ie>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	"Daniel Vetter" <daniel.vetter@intel.com>
Subject: Re: [Intel-gfx] [PATCH v4 0/6] Finally fix watermarks
Date: Thu, 28 Jul 2016 17:03:52 -0700	[thread overview]
Message-ID: <20160729000352.GR32025@intel.com> (raw)
In-Reply-To: <1469554483-24999-1-git-send-email-cpaul@redhat.com>

This is completely untested (and probably horribly broken/buggy), but
here's a quick mockup of the general approach I was thinking for
ensuring DDB & WM's can be updated together while ensuring the
three-step pipe flushing process is honored:

        https://github.com/mattrope/kernel/commits/experimental/lyude_ddb

Basically the idea is to take note of what's happening to the pipe's DDB
allocation (shrinking, growing, unchanged, etc.) during the atomic check
phase; then during the commit phase, we loop over the CRTC's three times
instead of just once, but only operate on a subset of the CRTC's in each
loop.  While operating on each CRTC, the plane, WM, and DDB all get
programmed together and have a single flush for all three.

Matt

On Tue, Jul 26, 2016 at 01:34:36PM -0400, Lyude wrote:
> Latest version of https://lkml.org/lkml/2016/7/26/290 . Resending the whole
> thing to keep it in one place.
> 
> Lyude (5):
>   drm/i915/skl: Add support for the SAGV, fix underrun hangs
>   drm/i915/skl: Only flush pipes when we change the ddb allocation
>   drm/i915/skl: Fix extra whitespace in skl_flush_wm_values()
>   drm/i915/skl: Update plane watermarks atomically during plane updates
>   drm/i915/skl: Always wait for pipes to update after a flush
> 
> Matt Roper (1):
>   drm/i915/gen9: Only copy WM results for changed pipes to skl_hw
> 
>  drivers/gpu/drm/i915/i915_drv.h      |   3 +
>  drivers/gpu/drm/i915/i915_reg.h      |   5 +
>  drivers/gpu/drm/i915/intel_display.c |  24 ++++
>  drivers/gpu/drm/i915/intel_drv.h     |   4 +
>  drivers/gpu/drm/i915/intel_pm.c      | 240 +++++++++++++++++++++++++++++++----
>  drivers/gpu/drm/i915/intel_sprite.c  |   2 +
>  6 files changed, 255 insertions(+), 23 deletions(-)
> 
> -- 
> 2.7.4
> 
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-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795