From 64989ca4b27acb026b6496ec21e43bee66f86a5b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Fri, 13 May 2016 20:53:56 +0300 Subject: [PATCH] drm/i915: Refresh cached DP port register value on resume MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit During hibernation the cached DP port register value will be left with whatever value we have there when we create the hibernation image. Currently that means the port (and eDP PLL) will be off in the cached value. However when we resume there is no guarantee that the value in the actual register will match the cached value. If i915 isn't loaded in the kernel that loads the hibernation image, the port may well be on (eg. left on by the BIOS). The encoder state readout does the right thing in this case and updates our encoder state to reflect the actual hardware state. However the post-resume modeset will then use the stale cached port register value in intel_dp_link_down() and potentially confuse the hardware. This was caught by the following assert WARNING: CPU: 3 PID: 5288 at ../drivers/gpu/drm/i915/intel_dp.c:2184 assert_edp_pll+0x99/0xa0 [i915] eDP PLL state assertion failure (expected on, current off) on account of the eDP PLL getting prematurely turned off when shutting down the port, since the DP_PLL_ENABLE bit wasn't set in the cached register value. Presumably I introduced this problem in commit 6fec76628333 ("drm/i915: Use intel_dp->DP in eDP PLL setup") as before that we didn't update the cached value after shuttting the port down. That's assuming the port got enabled at least once prior to hibernating. If that didn't happen then the cached value would still have been totally out of sync with reality (eg. first boot w/o eDP on, then hibernate, and then resume with eDP on). So, let's fix this properly and refresh the cached register value from the hardware register during resume. DDI platforms shouldn't use the cached value during port disable at least, so shouldn't have this particular issue. They might still have issues if we skip the initial modeset and then try to retrain the link or something. But untangling this DP vs. DDI mess is a bigger topic, so let's jut punt on DDI for now. Cc: Jani Nikula Cc: stable@vger.kernel.org Fixes: 6fec76628333 ("drm/i915: Use intel_dp->DP in eDP PLL setup") Signed-off-by: Ville Syrjälä Link: http://patchwork.freedesktop.org/patch/msgid/1463162036-27931-1-git-send-email-ville.syrjala@linux.intel.com Reviewed-by: Imre Deak --- drivers/gpu/drm/i915/intel_dp.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c index 9a1a347146dd..8bb20e7048ec 100644 --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -4618,13 +4618,15 @@ static void intel_edp_panel_vdd_sanitize(struct intel_dp *intel_dp) void intel_dp_encoder_reset(struct drm_encoder *encoder) { - struct intel_dp *intel_dp; + struct drm_i915_private *dev_priv = to_i915(encoder->dev); + struct intel_dp *intel_dp = enc_to_intel_dp(encoder); + + if (!HAS_DDI(dev_priv)) + intel_dp->DP = I915_READ(intel_dp->output_reg); if (to_intel_encoder(encoder)->type != INTEL_OUTPUT_EDP) return; - intel_dp = enc_to_intel_dp(encoder); - pps_lock(intel_dp); /*