From 15160879d47213c32f357bc67b6014d9aaf14ed7 Mon Sep 17 00:00:00 2001 From: Tvrtko Ursulin Date: Wed, 17 Jul 2019 19:06:19 +0100 Subject: [PATCH] drm/i915: Fix GEN8_MCR_SELECTOR programming fls returns bit positions starting from one for the lsb and the MCR register expects zero based (sub)slice addressing. Incorrent MCR programming can have the effect of directing MMIO reads of registers in the 0xb100-0xb3ff range to invalid subslice returning zeroes instead of actual content. Signed-off-by: Tvrtko Ursulin Fixes: 1e40d4aea57b ("drm/i915/cnl: Implement WaProgramMgsrForCorrectSliceSpecificMmioReads") Reviewed-by: Chris Wilson Link: https://patchwork.freedesktop.org/patch/msgid/20190717180624.20354-2-tvrtko.ursulin@linux.intel.com --- drivers/gpu/drm/i915/gt/intel_engine_cs.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c index c0bc9cb..6f93caf 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c @@ -962,9 +962,14 @@ const char *i915_cache_level_str(struct drm_i915_private *i915, int type) u32 intel_calculate_mcr_s_ss_select(struct drm_i915_private *dev_priv) { const struct sseu_dev_info *sseu = &RUNTIME_INFO(dev_priv)->sseu; + unsigned int slice = fls(sseu->slice_mask) - 1; + unsigned int subslice; u32 mcr_s_ss_select; - u32 slice = fls(sseu->slice_mask); - u32 subslice = fls(sseu->subslice_mask[slice]); + + GEM_BUG_ON(slice >= ARRAY_SIZE(sseu->subslice_mask)); + subslice = fls(sseu->subslice_mask[slice]); + GEM_BUG_ON(!subslice); + subslice--; if (IS_GEN(dev_priv, 10)) mcr_s_ss_select = GEN8_MCR_SLICE(slice) | -- 2.7.4