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

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Date:	Fri, 25 Sep 2015 19:26:13 -0700
From:	Brian Norris <briannorris@...omium.org>
To:	<intel-gfx@...ts.freedesktop.org>
Cc:	<linux-kernel@...r.kernel.org>,
	Brian Norris <computersforpeace@...il.com>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Stéphane Marchesin <marcheu@...omium.org>,
	Duncan Laurie <dlaurie@...omium.org>,
	Brian Norris <briannorris@...omium.org>
Subject: [RFC PATCH] drm/i915: PSR regressions on Broadwell

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:

https://patchwork.freedesktop.org/patch/57698/

Signed-off-by: Brian Norris <briannorris@...omium.org>
---
 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;
-- 
2.6.0.rc2.230.g3dd15c0

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