Bay Trail devices are known to hang when changing the frequency often, this is discussed in great length in: https://bugzilla.kernel.org/show_bug.cgi?id=109051

Commit 6067a27d1f01 ("drm/i915: Avoid tweaking evaluation thresholds on Baytrail v3") is an attempt to workaround this. Several users in bko109051 report that an earlier version of this patch, v1: https://bugzilla.kernel.org/attachment.cgi?id=251471

Works better for them and they still see hangs with the merged v3.

Comparing the 2 versions shows that they are indeed not equivalent, v1 not only skips writing the GEN6_RP* registers from valleyview_set_rps, as v3 does. It also contained these modifications to i915_irq.c:

if (pm_iir & GEN6_PM_RP_DOWN_EI_EXPIRED) { if (!vlv_c0_above(dev_priv, &dev_priv->rps.down_ei, &now, - dev_priv->rps.down_threshold)) + VLV_RP_DOWN_EI_THRESHOLD)) events |= GEN6_PM_RP_DOWN_THRESHOLD; dev_priv->rps.down_ei = now; }

if (pm_iir & GEN6_PM_RP_UP_EI_EXPIRED) { if (vlv_c0_above(dev_priv, &dev_priv->rps.up_ei, &now, - dev_priv->rps.up_threshold)) + VLV_RP_UP_EI_THRESHOLD)) events |= GEN6_PM_RP_UP_THRESHOLD; dev_priv->rps.up_ei = now; }

Which use less aggressive up/down thresholds, which results in less GEN6_PM_RP_*_THRESHOLD events and thus in less calls to intel_set_rps() -> valleyview_set_rps() -> vlv_punit_write(PUNIT_REG_GPU_FREQ_REQ). With the last call being the likely cause of the hang.

This commit hardcodes the threshold_up and _down values for Bay Trail to less aggressive values, reducing the amount of clock frequency changes, thus avoiding the hangs some people are still seeing with the merged fix.

Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=109051 Signed-off-by: Hans de Goede hdegoede@redhat.com --- drivers/gpu/drm/i915/i915_reg.h | 3 +++ drivers/gpu/drm/i915/intel_pm.c | 5 ++++- 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h index 505c605eff98..acafc8408e43 100644 --- a/drivers/gpu/drm/i915/i915_reg.h +++ b/drivers/gpu/drm/i915/i915_reg.h @@ -1390,6 +1390,9 @@ enum i915_power_well_id { #define VLV_BIAS_CPU_125_SOC_875 (6 << 2) #define CHV_BIAS_CPU_50_SOC_50 (3 << 2)

+#define VLV_RP_UP_EI_THRESHOLD 90 +#define VLV_RP_DOWN_EI_THRESHOLD 70 + /* vlv2 north clock has */ #define CCK_FUSE_REG 0x8 #define CCK_FUSE_HPLL_FREQ_MASK 0x3 diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c index 1db79a860b96..b06379622301 100644 --- a/drivers/gpu/drm/i915/intel_pm.c +++ b/drivers/gpu/drm/i915/intel_pm.c @@ -6116,8 +6116,11 @@ static void gen6_set_rps_thresholds(struct drm_i915_private *dev_priv, u8 val) /* When byt can survive without system hang with dynamic * sw freq adjustments, this restriction can be lifted. */ - if (IS_VALLEYVIEW(dev_priv)) + if (IS_VALLEYVIEW(dev_priv)) { + threshold_up = VLV_RP_UP_EI_THRESHOLD; + threshold_down = VLV_RP_DOWN_EI_THRESHOLD; goto skip_hw_write; + }

I915_WRITE(GEN6_RP_UP_EI, GT_INTERVAL_FROM_US(dev_priv, ei_up));