+++ /dev/null
-From 21556350ade3cb5d7afecc8b3544e56431d21695 Mon Sep 17 00:00:00 2001
-From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
-Date: Wed, 14 Nov 2018 19:34:40 +0200
-Subject: drm/i915: Disable LP3 watermarks on all SNB machines
-MIME-Version: 1.0
-Content-Type: text/plain; charset=UTF-8
-Content-Transfer-Encoding: 8bit
-
-From: Ville Syrjälä <ville.syrjala@linux.intel.com>
-
-commit 21556350ade3cb5d7afecc8b3544e56431d21695 upstream.
-
-I have a Thinkpad X220 Tablet in my hands that is losing vblank
-interrupts whenever LP3 watermarks are used.
-
-If I nudge the latency value written to the WM3 register just
-by one in either direction the problem disappears. That to me
-suggests that the punit will not enter the corrsponding
-powersave mode (MPLL shutdown IIRC) unless the latency value
-in the register matches exactly what we read from SSKPD. Ie.
-it's not really a latency value but rather just a cookie
-by which the punit can identify the desired power saving state.
-On HSW/BDW this was changed such that we actually just write
-the WM level number into those bits, which makes much more
-sense given the observed behaviour.
-
-We could try to handle this by disallowing LP3 watermarks
-only when vblank interrupts are enabled but we'd first have
-to prove that only vblank interrupts are affected, which
-seems unlikely. Also we can't grab the wm mutex from the
-vblank enable/disable hooks because those are called with
-various spinlocks held. Thus we'd have to redesigne the
-watermark locking. So to play it safe and keep the code
-simple we simply disable LP3 watermarks on all SNB machines.
-
-To do that we simply zero out the latency values for
-watermark level 3, and we adjust the watermark computation
-to check for that. The behaviour now matches that of the
-g4x/vlv/skl wm code in the presence of a zeroed latency
-value.
-
-v2: s/USHRT_MAX/U32_MAX/ for consistency with the types (Chris)
-
-Cc: stable@vger.kernel.org
-Cc: Chris Wilson <chris@chris-wilson.co.uk>
-Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
-Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101269
-Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103713
-Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
-Link: https://patchwork.freedesktop.org/patch/msgid/20181114173440.6730-1-ville.syrjala@linux.intel.com
-(cherry picked from commit 03981c6ebec4fc7056b9b45f847393aeac90d060)
-Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
-Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-
----
- drivers/gpu/drm/i915/intel_pm.c | 41 +++++++++++++++++++++++++++++++++++++++-
- 1 file changed, 40 insertions(+), 1 deletion(-)
-
---- a/drivers/gpu/drm/i915/intel_pm.c
-+++ b/drivers/gpu/drm/i915/intel_pm.c
-@@ -2500,6 +2500,9 @@ static uint32_t ilk_compute_spr_wm(const
- uint32_t method1, method2;
- int cpp;
-
-+ if (mem_value == 0)
-+ return U32_MAX;
-+
- if (!intel_wm_plane_visible(cstate, pstate))
- return 0;
-
-@@ -2523,6 +2526,9 @@ static uint32_t ilk_compute_cur_wm(const
- {
- int cpp;
-
-+ if (mem_value == 0)
-+ return U32_MAX;
-+
- if (!intel_wm_plane_visible(cstate, pstate))
- return 0;
-
-@@ -2540,6 +2546,9 @@ static uint32_t ilk_compute_fbc_wm(const
- {
- int cpp;
-
-+ if (mem_value == 0)
-+ return U32_MAX;
-+
- if (!intel_wm_plane_visible(cstate, pstate))
- return 0;
-
-@@ -2981,6 +2990,34 @@ static void snb_wm_latency_quirk(struct
- 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)
-+{
-+ /*
-+ * On some SNB machines (Thinkpad X220 Tablet at least)
-+ * LP3 usage can cause vblank interrupts to be lost.
-+ * The DEIIR bit will go high but it looks like the CPU
-+ * never gets interrupted.
-+ *
-+ * It's not clear whether other interrupt source could
-+ * be affected or if this is somehow limited to vblank
-+ * 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;
-+
-+ 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_setup_wm_latency(struct drm_i915_private *dev_priv)
- {
- intel_read_wm_latency(dev_priv, dev_priv->wm.pri_latency);
-@@ -2997,8 +3034,10 @@ static void ilk_setup_wm_latency(struct
- intel_print_wm_latency(dev_priv, "Sprite", dev_priv->wm.spr_latency);
- intel_print_wm_latency(dev_priv, "Cursor", dev_priv->wm.cur_latency);
-
-- if (IS_GEN6(dev_priv))
-+ if (IS_GEN6(dev_priv)) {
- snb_wm_latency_quirk(dev_priv);
-+ snb_wm_lp3_irq_quirk(dev_priv);
-+ }
- }
-
- static void skl_setup_wm_latency(struct drm_i915_private *dev_priv)
projects / thirdparty / kernel / stable-queue.git / commitdiff
