drm/i915: Trust programmed MCR in read_subslice_reg

Instead of re-calculating the MCR selector in read_subslice_reg do the
rwm on its existing value and restore it when done.

This consolidates MCR programming to one place for cnl+, and avoids
re-calculating its default value on older platforms during hangcheck.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190717180624.20354-3-tvrtko.ursulin@linux.intel.com

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index 6f93caf..cc4d182 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -989,27 +989,17 @@ read_subslice_reg(struct intel_engine_cs *engine, int slice, int subslice,
 {
        struct drm_i915_private *i915 = engine->i915;
        struct intel_uncore *uncore = engine->uncore;
-       u32 mcr_slice_subslice_mask;
-       u32 mcr_slice_subslice_select;
-       u32 default_mcr_s_ss_select;
-       u32 mcr;
-       u32 ret;
+       u32 mcr_mask, mcr_ss, mcr, old_mcr, val;
        enum forcewake_domains fw_domains;
 
        if (INTEL_GEN(i915) >= 11) {
-               mcr_slice_subslice_mask = GEN11_MCR_SLICE_MASK |
-                                         GEN11_MCR_SUBSLICE_MASK;
-               mcr_slice_subslice_select = GEN11_MCR_SLICE(slice) |
-                                           GEN11_MCR_SUBSLICE(subslice);
+               mcr_mask = GEN11_MCR_SLICE_MASK | GEN11_MCR_SUBSLICE_MASK;
+               mcr_ss = GEN11_MCR_SLICE(slice) | GEN11_MCR_SUBSLICE(subslice);
        } else {
-               mcr_slice_subslice_mask = GEN8_MCR_SLICE_MASK |
-                                         GEN8_MCR_SUBSLICE_MASK;
-               mcr_slice_subslice_select = GEN8_MCR_SLICE(slice) |
-                                           GEN8_MCR_SUBSLICE(subslice);
+               mcr_mask = GEN8_MCR_SLICE_MASK | GEN8_MCR_SUBSLICE_MASK;
+               mcr_ss = GEN8_MCR_SLICE(slice) | GEN8_MCR_SUBSLICE(subslice);
        }
 
-       default_mcr_s_ss_select = intel_calculate_mcr_s_ss_select(i915);
-
        fw_domains = intel_uncore_forcewake_for_reg(uncore, reg,
                                                    FW_REG_READ);
        fw_domains |= intel_uncore_forcewake_for_reg(uncore,
@@ -1019,26 +1009,23 @@ read_subslice_reg(struct intel_engine_cs *engine, int slice, int subslice,
        spin_lock_irq(&uncore->lock);
        intel_uncore_forcewake_get__locked(uncore, fw_domains);
 
-       mcr = intel_uncore_read_fw(uncore, GEN8_MCR_SELECTOR);
-
-       WARN_ON_ONCE((mcr & mcr_slice_subslice_mask) !=
-                    default_mcr_s_ss_select);
+       old_mcr = mcr = intel_uncore_read_fw(uncore, GEN8_MCR_SELECTOR);
 
-       mcr &= ~mcr_slice_subslice_mask;
-       mcr |= mcr_slice_subslice_select;
+       mcr &= ~mcr_mask;
+       mcr |= mcr_ss;
        intel_uncore_write_fw(uncore, GEN8_MCR_SELECTOR, mcr);
 
-       ret = intel_uncore_read_fw(uncore, reg);
+       val = intel_uncore_read_fw(uncore, reg);
 
-       mcr &= ~mcr_slice_subslice_mask;
-       mcr |= default_mcr_s_ss_select;
+       mcr &= ~mcr_mask;
+       mcr |= old_mcr & mcr_mask;
 
        intel_uncore_write_fw(uncore, GEN8_MCR_SELECTOR, mcr);
 
        intel_uncore_forcewake_put__locked(uncore, fw_domains);
        spin_unlock_irq(&uncore->lock);
 
-       return ret;
+       return val;
 }
 
 /* NB: please notice the memset */