From 9b18572e83bfd5378b3fcff3acf123f7bddf558a Mon Sep 17 00:00:00 2001 From: Mika Kuoppala Date: Thu, 18 Feb 2016 17:58:09 +0200 Subject: [PATCH] drm/i915/gen9: Verify and enforce dc6 state writes It has been observed that sometimes disabling the dc6 fails and dc6 state pops back up, brief moment after disabling. This has to be dmc save/restore timing issue or other bug in the way dc states are handled. Try to work around this issue as we don't have firmware fix yet available. Verify that the value we wrote for the dmc sticks, and also enforce it by rewriting it, if it didn't. v2: Zero rereads on rewrite for extra paranoia (Imre) Testcase: kms_flip/basic-flip-vs-dpms References: https://bugs.freedesktop.org/show_bug.cgi?id=93768 Cc: Patrik Jakobsson Cc: Rodrigo Vivi Cc: Imre Deak Signed-off-by: Mika Kuoppala Reviewed-by: Imre Deak Signed-off-by: Imre Deak Link: http://patchwork.freedesktop.org/patch/msgid/1455811089-27884-1-git-send-email-mika.kuoppala@intel.com (cherry picked from commit 779cb5d3ddd72950ec726f86e38f7575c7fbdd4c) Signed-off-by: Jani Nikula --- drivers/gpu/drm/i915/intel_runtime_pm.c | 41 +++++++++++++++++++++++-- 1 file changed, 39 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c index 19e6ff64ce9d..678ed3475d7e 100644 --- a/drivers/gpu/drm/i915/intel_runtime_pm.c +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c @@ -470,6 +470,43 @@ static void gen9_set_dc_state_debugmask_memory_up( } } +static void gen9_write_dc_state(struct drm_i915_private *dev_priv, + u32 state) +{ + int rewrites = 0; + int rereads = 0; + u32 v; + + I915_WRITE(DC_STATE_EN, state); + + /* It has been observed that disabling the dc6 state sometimes + * doesn't stick and dmc keeps returning old value. Make sure + * the write really sticks enough times and also force rewrite until + * we are confident that state is exactly what we want. + */ + do { + v = I915_READ(DC_STATE_EN); + + if (v != state) { + I915_WRITE(DC_STATE_EN, state); + rewrites++; + rereads = 0; + } else if (rereads++ > 5) { + break; + } + + } while (rewrites < 100); + + if (v != state) + DRM_ERROR("Writing dc state to 0x%x failed, now 0x%x\n", + state, v); + + /* Most of the times we need one retry, avoid spam */ + if (rewrites > 1) + DRM_DEBUG_KMS("Rewrote dc state to 0x%x %d times\n", + state, rewrites); +} + static void gen9_set_dc_state(struct drm_i915_private *dev_priv, uint32_t state) { uint32_t val; @@ -502,8 +539,8 @@ static void gen9_set_dc_state(struct drm_i915_private *dev_priv, uint32_t state) val &= ~mask; val |= state; - I915_WRITE(DC_STATE_EN, val); - POSTING_READ(DC_STATE_EN); + + gen9_write_dc_state(dev_priv, val); dev_priv->csr.dc_state = val & mask; } -- 2.20.1