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    Subject[PATCH 3.16 013/136] drm/i915: Read timings from the correct transcoder in intel_crtc_mode_get()
    3.16.54-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

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

    commit e30a154b5262b967b133b06ac40777e651045898 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().

    Cc: dri-devel@lists.freedesktop.org
    Cc: Rob Kramer <rob@solution-space.com>
    Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
    Reported-by: Rob Kramer <rob@solution-space.com>
    Fixes: eccb140bca67 ("drm/i915: hw state readout&check support for cpu_transcoder")
    References: https://lists.freedesktop.org/archives/dri-devel/2016-April/104142.html
    Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
    Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
    Link: https://patchwork.freedesktop.org/patch/msgid/1459525046-19425-1-git-send-email-ville.syrjala@linux.intel.com
    [bwh: Backported to 3.16: pipe_config is a struct not a pointer]
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/gpu/drm/i915/intel_display.c | 14 +++++++++-----
    1 file changed, 9 insertions(+), 5 deletions(-)

    --- a/drivers/gpu/drm/i915/intel_display.c
    +++ b/drivers/gpu/drm/i915/intel_display.c
    @@ -8662,13 +8662,10 @@ struct drm_display_mode *intel_crtc_mode
    {
    struct drm_i915_private *dev_priv = dev->dev_private;
    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_config 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);
    @@ -8690,6 +8687,13 @@ 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;
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