On 05/26/2015 10:22 AM, [email protected] wrote:
From: Ville Syrjälä <[email protected]>
Switch from using 31 PFI credits to 63 PFI credits when cdclk>=czclk on
CHV. The spec lists both 31 and 63 as "suggested" values, but based on
feedback from hardware folks we should actually be using 63. Originally
I picked the 31 basically by flipping a coin.
Signed-off-by: Ville Syrjälä <[email protected]>
---
drivers/gpu/drm/i915/intel_display.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/intel_display.c
b/drivers/gpu/drm/i915/intel_display.c
index 067b1de..44b9c54 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5986,7 +5986,7 @@ static void vlv_program_pfi_credits(struct
drm_i915_private *dev_priv)
if (DIV_ROUND_CLOSEST(dev_priv->cdclk_freq, 1000) >=
dev_priv->rps.cz_freq) {
/* CHV suggested value is 31 or 63 */
if (IS_CHERRYVIEW(dev_priv))
- credits = PFI_CREDIT_31;
+ credits = PFI_CREDIT_63;
else
credits = PFI_CREDIT(15);
} else {
Although not part of this review the else clause is setting PFI_CREDIT
to 15 when the BPSEC states that the default of 8 should be used when
cdclk/czclk < 1. According to the original patch, 15 is the optimal
value as stated by another driver team.
Reviewed-by: Clint Taylor <[email protected]>
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