This is a note to let you know that I've just added the patch titled

drm/i915: Fix vblank timestamp/frame counter jumps on gen2

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: drm-i915-fix-vblank-timestamp-frame-counter-jumps-on-gen2.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From a87e55f89f0b0dc541d89248a8445635936a3858 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= ville.syrjala@linux.intel.com Date: Wed, 29 Nov 2017 17:37:30 +0200 Subject: drm/i915: Fix vblank timestamp/frame counter jumps on gen2 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

From: Ville Syrjälä ville.syrjala@linux.intel.com

commit a87e55f89f0b0dc541d89248a8445635936a3858 upstream.

Previously I was under the impression that the scanline counter reads 0 when the pipe is off. Turns out that's not correct, and instead the scanline counter simply stops when the pipe stops, and it retains it's last value until the pipe starts up again, at which point the scanline counter jumps to vblank start.

These jumps can cause the timestamp to jump backwards by one frame. Since we use the timestamps to guesstimage also the frame counter value on gen2, that would cause the frame counter to also jump backwards, which leads to a massice difference from the previous value. The end result is that flips/vblank events don't appear to complete as they're stuck waiting for the frame counter to catch up to that massive difference.

Fix the problem properly by actually making sure the scanline counter has started to move before we assume that it's safe to enable vblank processing.

v2: Less pointless duplication in the code (Chris)

Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Chris Wilson chris@chris-wilson.co.uk Reviewed-by: Chris Wilson chris@chris-wilson.co.uk Fixes: b7792d8b54cc ("drm/i915: Wait for pipe to start before sampling vblank timestamps on gen2") Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20171129153732.3612-1-ville.sy... (cherry picked from commit 8fedd64dabc86d0f31a0d1e152be3aa23c323553) Signed-off-by: Joonas Lahtinen joonas.lahtinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- drivers/gpu/drm/i915/intel_display.c | 53 +++++++++++++++++++++++------------ 1 file changed, 36 insertions(+), 17 deletions(-)

--- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -1000,7 +1000,8 @@ enum transcoder intel_pipe_to_cpu_transc return crtc->config->cpu_transcoder; }

-static bool pipe_dsl_stopped(struct drm_i915_private *dev_priv, enum pipe pipe) +static bool pipe_scanline_is_moving(struct drm_i915_private *dev_priv, + enum pipe pipe) { i915_reg_t reg = PIPEDSL(pipe); u32 line1, line2; @@ -1015,7 +1016,28 @@ static bool pipe_dsl_stopped(struct drm_ msleep(5); line2 = I915_READ(reg) & line_mask;

- return line1 == line2; + return line1 != line2; +} + +static void wait_for_pipe_scanline_moving(struct intel_crtc *crtc, bool state) +{ + struct drm_i915_private *dev_priv = to_i915(crtc->base.dev); + enum pipe pipe = crtc->pipe; + + /* Wait for the display line to settle/start moving */ + if (wait_for(pipe_scanline_is_moving(dev_priv, pipe) == state, 100)) + DRM_ERROR("pipe %c scanline %s wait timed out\n", + pipe_name(pipe), onoff(state)); +} + +static void intel_wait_for_pipe_scanline_stopped(struct intel_crtc *crtc) +{ + wait_for_pipe_scanline_moving(crtc, false); +} + +static void intel_wait_for_pipe_scanline_moving(struct intel_crtc *crtc) +{ + wait_for_pipe_scanline_moving(crtc, true); }

/* @@ -1038,7 +1060,6 @@ static void intel_wait_for_pipe_off(stru { struct drm_i915_private *dev_priv = to_i915(crtc->base.dev); enum transcoder cpu_transcoder = crtc->config->cpu_transcoder; - enum pipe pipe = crtc->pipe;

if (INTEL_GEN(dev_priv) >= 4) { i915_reg_t reg = PIPECONF(cpu_transcoder); @@ -1049,9 +1070,7 @@ static void intel_wait_for_pipe_off(stru 100)) WARN(1, "pipe_off wait timed out\n"); } else { - /* Wait for the display line to settle */ - if (wait_for(pipe_dsl_stopped(dev_priv, pipe), 100)) - WARN(1, "pipe_off wait timed out\n"); + intel_wait_for_pipe_scanline_stopped(crtc); } }

@@ -1944,15 +1963,14 @@ static void intel_enable_pipe(struct int POSTING_READ(reg);

/* - * Until the pipe starts DSL will read as 0, which would cause - * an apparent vblank timestamp jump, which messes up also the - * frame count when it's derived from the timestamps. So let's - * wait for the pipe to start properly before we call - * drm_crtc_vblank_on() - */ - if (dev->max_vblank_count == 0 && - wait_for(intel_get_crtc_scanline(crtc) != crtc->scanline_offset, 50)) - DRM_ERROR("pipe %c didn't start\n", pipe_name(pipe)); + * Until the pipe starts PIPEDSL reads will return a stale value, + * which causes an apparent vblank timestamp jump when PIPEDSL + * resets to its proper value. That also messes up the frame count + * when it's derived from the timestamps. So let's wait for the + * pipe to start properly before we call drm_crtc_vblank_on() + */ + if (dev->max_vblank_count == 0) + intel_wait_for_pipe_scanline_moving(crtc); }

/** @@ -14682,6 +14700,8 @@ void i830_enable_pipe(struct drm_i915_pr

void i830_disable_pipe(struct drm_i915_private *dev_priv, enum pipe pipe) { + struct intel_crtc *crtc = intel_get_crtc_for_pipe(dev_priv, pipe); + DRM_DEBUG_KMS("disabling pipe %c due to force quirk\n", pipe_name(pipe));

@@ -14691,8 +14711,7 @@ void i830_disable_pipe(struct drm_i915_p I915_WRITE(PIPECONF(pipe), 0); POSTING_READ(PIPECONF(pipe));

- if (wait_for(pipe_dsl_stopped(dev_priv, pipe), 100)) - DRM_ERROR("pipe %c off wait timed out\n", pipe_name(pipe)); + intel_wait_for_pipe_scanline_stopped(crtc);

I915_WRITE(DPLL(pipe), DPLL_VGA_MODE_DIS); POSTING_READ(DPLL(pipe));

Patches currently in stable-queue which might be from ville.syrjala@linux.intel.com are

queue-4.14/drm-i915-fix-vblank-timestamp-frame-counter-jumps-on-gen2.patch