Patch "drm/i915: Read timings from the correct transcoder in intel_crtc_mode_get()" has been added to the 4.13-stable tree

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

drm/i915: Read timings from the correct transcoder in intel_crtc_mode_get()

to the 4.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-i915-read-timings-from-the-correct-transcoder-in-intel_crtc_mode_get.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <[email protected]>
Date: Fri, 1 Apr 2016 18:37:25 +0300
Subject: drm/i915: Read timings from the correct transcoder in intel_crtc_mode_get()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Ville Syrjälä <[email protected]>

commit 7b50f7b24cd6c98541f1af53bddc5b6e861ee8c8 upstream.

intel_crtc->config->cpu_transcoder isn't yet filled out when intel_crtc_mode_get() gets called during output probing, so we should not use it there. Instead intel_crtc_mode_get() figures out the correct transcoder on its own, and that's what we should use.

If the BIOS boots LVDS on pipe B, intel_crtc_mode_get() would actually end up reading the timings from pipe A instead (since PIPE_A==0), which clearly isn't what we want.

It looks to me like this may have been broken by
commit eccb140bca67 ("drm/i915: hw state readout&check support for cpu_transcoder") as that one removed the early initialization of cpu_transcoder from intel_crtc_init().

References: https://lists.freedesktop.org/archives/dri-devel/2016-April/104142.html

---
 drivers/gpu/drm/i915/intel_display.c |   14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

@@ -10059,13 +10059,10 @@ struct drm_display_mode *intel_crtc_mode
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
-	enum transcoder cpu_transcoder = intel_crtc->config->cpu_transcoder;
+	enum transcoder cpu_transcoder;
 	struct drm_display_mode *mode;
 	struct intel_crtc_state *pipe_config;
-	int htot = I915_READ(HTOTAL(cpu_transcoder));
-	int hsync = I915_READ(HSYNC(cpu_transcoder));
-	int vtot = I915_READ(VTOTAL(cpu_transcoder));
-	int vsync = I915_READ(VSYNC(cpu_transcoder));
+	u32 htot, hsync, vtot, vsync;
 	enum pipe pipe = intel_crtc->pipe;
 
 	mode = kzalloc(sizeof(*mode), GFP_KERNEL);

@@ -10093,6 +10090,13 @@ struct drm_display_mode *intel_crtc_mode
 	i9xx_crtc_clock_get(intel_crtc, pipe_config);
 
 	mode->clock = pipe_config->port_clock / pipe_config->pixel_multiplier;
+
+	cpu_transcoder = pipe_config->cpu_transcoder;
+	htot = I915_READ(HTOTAL(cpu_transcoder));
+	hsync = I915_READ(HSYNC(cpu_transcoder));
+	vtot = I915_READ(VTOTAL(cpu_transcoder));
+	vsync = I915_READ(VSYNC(cpu_transcoder));
+
 	mode->hdisplay = (htot & 0xffff) + 1;
 	mode->htotal = ((htot & 0xffff0000) >> 16) + 1;
 	mode->hsync_start = (hsync & 0xffff) + 1;

Patches currently in stable-queue which might be from [email protected] are

queue-4.13/drm-i915-bios-parse-ddi-ports-also-for-chv-for-hdmi-ddc-pin-and-dp-aux-channel.patch queue-4.13/drm-i915-read-timings-from-the-correct-transcoder-in-intel_crtc_mode_get.patch