From: Tvrtko Ursulin <tvrtko.ursu...@intel.com> We can implement limited RC6 counter wrap-around protection under the assumption that clients will be reading this value more frequently than the wrap period on a given platform.
With the typical wrap-around period being ~90 minutes, even with the exception of Baytrail which wraps every 13 seconds, this sounds like a reasonable assumption. Implementation works by storing a 64-bit software copy of a hardware RC6 counter, along with the previous HW counter snapshot. This enables it to detect wrap is polled frequently enough and keep the software copy monotonically incrementing. v2: * Missed GEN6_GT_GFX_RC6_LOCKED when considering slot sizing and indexing. * Fixed off-by-one in wrap-around handling. (Chris Wilson) v3: * Simplify index checking by using unsigned int. (Chris Wilson) * Expand the comment to explain why indexing works. v4: * Use __int128 if supported. v5: * Use mul_u64_u32_div. (Chris Wilson) Signed-off-by: Tvrtko Ursulin <tvrtko.ursu...@intel.com> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94852 Cc: Chris Wilson <ch...@chris-wilson.co.uk> Reviewed-by: Chris Wilson <ch...@chris-wilson.co.uk> # v3 Cc: Ville Syrjälä <ville.syrj...@linux.intel.com> --- drivers/gpu/drm/i915/i915_drv.h | 2 ++ drivers/gpu/drm/i915/intel_pm.c | 64 ++++++++++++++++++++++++++++++++++------- 2 files changed, 56 insertions(+), 10 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index ad1fc845cd1b..28a2671a26c7 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -946,6 +946,8 @@ struct intel_rps { struct intel_rc6 { bool enabled; + u64 prev_hw_residency[4]; + u64 cur_residency[4]; }; struct intel_llc_pstate { diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c index 41f26ab46501..b10f67338c0e 100644 --- a/drivers/gpu/drm/i915/intel_pm.c +++ b/drivers/gpu/drm/i915/intel_pm.c @@ -9417,15 +9417,16 @@ static u64 vlv_residency_raw(struct drm_i915_private *dev_priv, const i915_reg_t reg) { u32 lower, upper, tmp; - unsigned long flags; int loop = 2; - /* The register accessed do not need forcewake. We borrow + /* + * The register accessed do not need forcewake. We borrow * uncore lock to prevent concurrent access to range reg. */ - spin_lock_irqsave(&dev_priv->uncore.lock, flags); + lockdep_assert_held(&dev_priv->uncore.lock); - /* vlv and chv residency counters are 40 bits in width. + /* + * vlv and chv residency counters are 40 bits in width. * With a control bit, we can choose between upper or lower * 32bit window into this counter. * @@ -9449,29 +9450,49 @@ static u64 vlv_residency_raw(struct drm_i915_private *dev_priv, upper = I915_READ_FW(reg); } while (upper != tmp && --loop); - /* Everywhere else we always use VLV_COUNTER_CONTROL with the + /* + * Everywhere else we always use VLV_COUNTER_CONTROL with the * VLV_COUNT_RANGE_HIGH bit set - so it is safe to leave it set * now. */ - spin_unlock_irqrestore(&dev_priv->uncore.lock, flags); - return lower | (u64)upper << 8; } u64 intel_rc6_residency_ns(struct drm_i915_private *dev_priv, const i915_reg_t reg) { - u64 time_hw; + u64 time_hw, prev_hw, overflow_hw; + unsigned int fw_domains; + unsigned long flags; + unsigned int i; u32 mul, div; if (!HAS_RC6(dev_priv)) return 0; + /* + * Store previous hw counter values for counter wrap-around handling. + * + * There are only four interesting registers and they live next to each + * other so we can use the relative address, compared to the smallest + * one as the index into driver storage. + */ + i = (i915_mmio_reg_offset(reg) - + i915_mmio_reg_offset(GEN6_GT_GFX_RC6_LOCKED)) / sizeof(u32); + if (WARN_ON_ONCE(i >= ARRAY_SIZE(dev_priv->gt_pm.rc6.cur_residency))) + return 0; + + fw_domains = intel_uncore_forcewake_for_reg(dev_priv, reg, FW_REG_READ); + + spin_lock_irqsave(&dev_priv->uncore.lock, flags); + intel_uncore_forcewake_get__locked(dev_priv, fw_domains); + /* On VLV and CHV, residency time is in CZ units rather than 1.28us */ if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv)) { mul = 1000000; div = dev_priv->czclk_freq; + overflow_hw = BIT_ULL(40); time_hw = vlv_residency_raw(dev_priv, reg); } else { /* 833.33ns units on Gen9LP, 1.28us elsewhere. */ @@ -9483,10 +9504,33 @@ u64 intel_rc6_residency_ns(struct drm_i915_private *dev_priv, div = 1; } - time_hw = I915_READ(reg); + overflow_hw = BIT_ULL(32); + time_hw = I915_READ_FW(reg); } - return DIV_ROUND_UP_ULL(time_hw * mul, div); + /* + * Counter wrap handling. + * + * But relying on a sufficient frequency of queries otherwise counters + * can still wrap. + */ + prev_hw = dev_priv->gt_pm.rc6.prev_hw_residency[i]; + dev_priv->gt_pm.rc6.prev_hw_residency[i] = time_hw; + + /* RC6 delta from last sample. */ + if (time_hw >= prev_hw) + time_hw -= prev_hw; + else + time_hw += overflow_hw - prev_hw; + + /* Add delta to RC6 extended raw driver copy. */ + time_hw += dev_priv->gt_pm.rc6.cur_residency[i]; + dev_priv->gt_pm.rc6.cur_residency[i] = time_hw; + + intel_uncore_forcewake_put__locked(dev_priv, fw_domains); + spin_unlock_irqrestore(&dev_priv->uncore.lock, flags); + + return mul_u64_u32_div(time_hw, mul, div); } u32 intel_get_cagf(struct drm_i915_private *dev_priv, u32 rpstat) -- 2.14.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
