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| author | Chris Wilson <chris@chris-wilson.co.uk> | 2019-09-17 11:00:29 +0300 |
|---|---|---|
| committer | Chris Wilson <chris@chris-wilson.co.uk> | 2019-09-17 17:25:40 +0300 |
| commit | 80fa64d62067ea7390cd27d924dcb7c028e455e9 (patch) | |
| tree | 3397c7bf0c495ccdcf133e5bdb0672e0f060f5be /drivers/gpu/drm/i915/intel_uncore.h | |
| parent | bb120e1171a966429287865134265811887daa6c (diff) | |
| download | linux-80fa64d62067ea7390cd27d924dcb7c028e455e9.tar.xz | |
drm/i915: Only apply a rmw mmio update if the value changes
If we try to clear, or even set, a bit in the register that doesn't
change the register state; skip the write. There's a slight danger in
that the register acts as a latch-on-write, but I do not think we use a
rmw cycle with any such latch registers.
Suggested-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190917080029.27632-1-chris@chris-wilson.co.uk
Diffstat (limited to 'drivers/gpu/drm/i915/intel_uncore.h')
| -rw-r--r-- | drivers/gpu/drm/i915/intel_uncore.h | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/drivers/gpu/drm/i915/intel_uncore.h b/drivers/gpu/drm/i915/intel_uncore.h index 414fc2cb0459..dcfa243892c6 100644 --- a/drivers/gpu/drm/i915/intel_uncore.h +++ b/drivers/gpu/drm/i915/intel_uncore.h @@ -378,23 +378,23 @@ intel_uncore_read64_2x32(struct intel_uncore *uncore, static inline void intel_uncore_rmw(struct intel_uncore *uncore, i915_reg_t reg, u32 clear, u32 set) { - u32 val; + u32 old, val; - val = intel_uncore_read(uncore, reg); - val &= ~clear; - val |= set; - intel_uncore_write(uncore, reg, val); + old = intel_uncore_read(uncore, reg); + val = (old & ~clear) | set; + if (val != old) + intel_uncore_write(uncore, reg, val); } static inline void intel_uncore_rmw_fw(struct intel_uncore *uncore, i915_reg_t reg, u32 clear, u32 set) { - u32 val; + u32 old, val; - val = intel_uncore_read_fw(uncore, reg); - val &= ~clear; - val |= set; - intel_uncore_write_fw(uncore, reg, val); + old = intel_uncore_read_fw(uncore, reg); + val = (old & ~clear) | set; + if (val != old) + intel_uncore_write_fw(uncore, reg, val); } static inline int intel_uncore_write_and_verify(struct intel_uncore *uncore, |