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Subject: Re: [PATCH v2 1/4] drm/i915/gen9: Only copy WM results for changed
 pipes to skl_hw
To: Lyude <cpaul@redhat.com>, intel-gfx@lists.freedesktop.org,
        Matt Roper <matthew.d.roper@intel.com>
References: <1469129020-2680-1-git-send-email-cpaul@redhat.com>
 <1469129020-2680-2-git-send-email-cpaul@redhat.com>
Cc: stable@vger.kernel.org,
        =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= <ville.syrjala@linux.intel.com>,
        Daniel Vetter <daniel.vetter@intel.com>,
        Radhakrishna Sripada <radhakrishna.sripada@intel.com>,
        Hans de Goede <hdegoede@redhat.com>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        David Airlie <airlied@linux.ie>, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org
From: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Message-ID: <d5bd1d1b-3d7b-7027-ea10-5b9313a3cf6a@linux.intel.com>
Date: Tue, 26 Jul 2016 16:21:20 +0200
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Op 21-07-16 om 21:23 schreef Lyude:
> From: Matt Roper <matthew.d.roper@intel.com>
>
> When we write watermark values to the hardware, those values are stored
> in dev_priv->wm.skl_hw.  However with recent watermark changes, the
> results structure we're copying from only contains valid watermark and
> DDB values for the pipes that are actually changing; the values for
> other pipes remain 0.  Thus a blind copy of the entire skl_wm_values
> structure will clobber the values for unchanged pipes...we need to be
> more selective and only copy over the values for the changing pipes.
>
> This mistake was hidden until recently due to another bug that caused us
> to erroneously re-calculate watermarks for all active pipes rather than
> changing pipes.  Only when that bug was fixed was the impact of this bug
> discovered (e.g., modesets failing with "Requested display configuration
> exceeds system watermark limitations" messages and leaving watermarks
> non-functional, even ones initiated by intel_fbdev_restore_mode).
>
> Changes since v1:
>  - Add a function for copying a pipe's wm values
>    (skl_copy_wm_for_pipe()) so we can reuse this later
>
> Fixes: 734fa01f3a17 ("drm/i915/gen9: Calculate watermarks during atomic 'check' (v2)")
> Fixes: 9b6130227495 ("drm/i915/gen9: Re-allocate DDB only for changed pipes")
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> Signed-off-by: Lyude <cpaul@redhat.com>
> Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
> Cc: stable@vger.kernel.org
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
> Cc: Hans de Goede <hdegoede@redhat.com>
Testcase: kms_cursor_legacy.2x-flip-vs-cursor-legacy

For patch 2/4 too probably.