[Intel-gfx] [PATCH 1/4] drm/i915: Disable LP1+ watermarks on Lenovo Thinkpad T431s

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

Lenovo Thinkpad T431s (ivb) apparently can't handle LP1+ watermarks
being enabled. It underruns severly enough that the screen is
unusable. The latency values and watemarks look as expected.
And sadly updating the BIOS to the latest version (BIOS GHET41WW
(1.26 ) 11/21/2018) did not help.

One glimmer of hope I had was the VBT. It seems to have some sort
of flag for "self refresh = yes/no", but when I looked at a bunch
of VBTs I had lying around most of them had that field set to "no".
So if we used that we'd end up disabling LP1+ on most machines.
That seems a bit harsh since we know LP1+ works just fine on
most machines.

Since I have no better ideas let's just disable LP1+ watermarks
on this particular machine via a quirk.

Cc: stable at vger.kernel.org
Cc: Andrea <andreatclist at gmail.com>
Reported-by: Andrea <andreatclist at gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109477
Fixes: a46a7350b1e8 ("drm/i915: Fix ilk+ watermarks when disabling pipes")
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 51 +++++++++++++++++++++++++--------
 1 file changed, 39 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 4c0e43caa5cd..75dceac19950 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3015,6 +3015,29 @@ static void snb_wm_latency_quirk(struct drm_i915_private *dev_priv)
 	intel_print_wm_latency(dev_priv, "Cursor", dev_priv->wm.cur_latency);
 }
 
+static void ilk_wm_disable_quirk(struct drm_i915_private *dev_priv,
+				 int level)
+{
+	int max_level = ilk_wm_max_level(dev_priv);
+
+	if (dev_priv->wm.pri_latency[level] == 0 &&
+	    dev_priv->wm.spr_latency[level] == 0 &&
+	    dev_priv->wm.cur_latency[level] == 0)
+		return;
+
+	DRM_DEBUG_KMS("LP%d+ watermarks disabled by quirk\n", level);
+
+	for (; level <= max_level; level++) {
+		dev_priv->wm.pri_latency[level] = 0;
+		dev_priv->wm.spr_latency[level] = 0;
+		dev_priv->wm.cur_latency[level] = 0;
+	}
+
+	intel_print_wm_latency(dev_priv, "Primary", dev_priv->wm.pri_latency);
+	intel_print_wm_latency(dev_priv, "Sprite", dev_priv->wm.spr_latency);
+	intel_print_wm_latency(dev_priv, "Cursor", dev_priv->wm.cur_latency);
+}
+
 static void snb_wm_lp3_irq_quirk(struct drm_i915_private *dev_priv)
 {
 	/*
@@ -3028,23 +3051,18 @@ static void snb_wm_lp3_irq_quirk(struct drm_i915_private *dev_priv)
 	 * interrupts only. To play it safe we disable LP3
 	 * watermarks entirely.
 	 */
-	if (dev_priv->wm.pri_latency[3] == 0 &&
-	    dev_priv->wm.spr_latency[3] == 0 &&
-	    dev_priv->wm.cur_latency[3] == 0)
-		return;
-
-	dev_priv->wm.pri_latency[3] = 0;
-	dev_priv->wm.spr_latency[3] = 0;
-	dev_priv->wm.cur_latency[3] = 0;
+	ilk_wm_disable_quirk(dev_priv, 3);
+}
 
-	DRM_DEBUG_KMS("LP3 watermarks disabled due to potential for lost interrupts\n");
-	intel_print_wm_latency(dev_priv, "Primary", dev_priv->wm.pri_latency);
-	intel_print_wm_latency(dev_priv, "Sprite", dev_priv->wm.spr_latency);
-	intel_print_wm_latency(dev_priv, "Cursor", dev_priv->wm.cur_latency);
+static void ilk_wm_disable_lp1_quirk(struct drm_i915_private *dev_priv)
+{
+	ilk_wm_disable_quirk(dev_priv, 1);
 }
 
 static void ilk_setup_wm_latency(struct drm_i915_private *dev_priv)
 {
+	struct pci_dev *pdev = dev_priv->drm.pdev;
+
 	intel_read_wm_latency(dev_priv, dev_priv->wm.pri_latency);
 
 	memcpy(dev_priv->wm.spr_latency, dev_priv->wm.pri_latency,
@@ -3063,6 +3081,15 @@ static void ilk_setup_wm_latency(struct drm_i915_private *dev_priv)
 		snb_wm_latency_quirk(dev_priv);
 		snb_wm_lp3_irq_quirk(dev_priv);
 	}
+
+	/*
+	 * Lenovo Thinkpad T431s (ivb)
+	 * Massive underruns.
+	 */
+	if (pdev->device == 0x0166 &&
+	    pdev->subsystem_vendor == 0x17aa &&
+	    pdev->subsystem_device == 0x2208)
+		ilk_wm_disable_lp1_quirk(dev_priv);
 }
 
 static void skl_setup_wm_latency(struct drm_i915_private *dev_priv)
-- 
2.19.2