[RFC PATCH] drm/i915: PSR regressions on Broadwell

From: Brian Norris
Date: Fri Sep 25 2015 - 22:27:24 EST

When using PSR, I see the screen freeze after only a few frames (sometimes a
split second; sometimes it seems like practically the first frame). Bisecting
led me to commit 3301d4092106 ("drm/i915: PSR: Fix DP_PSR_NO_TRAIN_ON_EXIT
logic") in v4.2. This patch is the simplest fix that gets it working again for
me, but it's probably wrong.

Random thought: perhaps my panel's DPCD is programmed incorrectly?

Anyway, any tips on fixing this properly?

Seen on Chromebook Pixel 2.

Also required this patch to get PSR properly running on 4.3-rc2:


Signed-off-by: Brian Norris <briannorris@xxxxxxxxxxxx>
drivers/gpu/drm/i915/intel_psr.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_psr.c b/drivers/gpu/drm/i915/intel_psr.c
index 7e335a8546f6..4cd33b76b8a6 100644
--- a/drivers/gpu/drm/i915/intel_psr.c
+++ b/drivers/gpu/drm/i915/intel_psr.c
@@ -261,7 +261,8 @@ static void hsw_psr_enable_source(struct intel_dp *intel_dp)
uint32_t val = 0x0;
const uint32_t link_entry_time = EDP_PSR_MIN_LINK_ENTRY_TIME_8_LINES;

- if (intel_dp->psr_dpcd[1] & DP_PSR_NO_TRAIN_ON_EXIT) {
+ if ((intel_dp->psr_dpcd[1] & DP_PSR_NO_TRAIN_ON_EXIT) &&
+ !IS_BROADWELL(dev)) {
/* It doesn't mean we shouldn't send TPS patters, so let's
send the minimal TP1 possible and skip TP2. */
val |= EDP_PSR_TP1_TIME_100us;

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