linux-kernel - Re: [PATCH AUTOSEL for 4.9 36/56] drm/i915: Fix the level 0 max

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Date:   Wed, 15 Nov 2017 13:08:05 +0200
From:   Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:     alexander.levin@...izon.com
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH AUTOSEL for 4.9 36/56] drm/i915: Fix the level 0 max_wm
 hack on VLV/CHV

On Wed, Nov 15, 2017 at 02:45:43AM +0000, alexander.levin@...izon.com wrote:
> From: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> 
> [ Upstream commit 1be4d3793d5a93daddcd9be657c429b38ad750a3 ]
> 
> The watermark should never exceed the FIFO size, so we need to
> check against the current FIFO size instead of the theoretical
> maximum when we clamp the level 0 watermark.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-4-git-send-email-ville.syrjala@linux.intel.com
> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
> Signed-off-by: Sasha Levin <alexander.levin@...izon.com>

Why are these patches being proposed for stable? They're not straight up
fixes for known issues, and there's always a chance that something will
break. Who is doing the qa on this?

> ---
>  drivers/gpu/drm/i915/intel_pm.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index ad5649259e6a..12bc608833cf 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -1129,13 +1129,13 @@ static void vlv_compute_wm(struct intel_crtc *crtc)
>  		/* normal watermarks */
>  		for (level = 0; level < wm_state->num_levels; level++) {
>  			int wm = vlv_compute_wm_level(plane, crtc, state, level);
> -			int max_wm = plane->base.type == DRM_PLANE_TYPE_CURSOR ? 63 : 511;
> +			int max_wm = plane->wm.fifo_size;
>  
>  			/* hack */
>  			if (WARN_ON(level == 0 && wm > max_wm))
>  				wm = max_wm;
>  
> -			if (wm > plane->wm.fifo_size)
> +			if (wm > max_wm)
>  				break;
>  
>  			switch (plane->base.type) {
> -- 
> 2.11.0

-- 
Ville Syrjälä
Intel OTC