On my Cherrytrail CUBE iwork8 Air tablet PIPE-A would get stuck on loading i915 at boot 1 out of every 3 boots, resulting in a non functional LCD. Once the i915 driver has successfully loaded, the panel can be disabled / enabled without hitting this issue. The getting stuck is caused by vlv_init_display_clock_gating() clearing the DPOUNIT_CLOCK_GATE_DISABLE bit in DSPCLK_GATE_D when called from chv_pipe_power_well_ops.enable() on driver load, while PIPE-A is enabled driving the DSI LCD by the BIOS. Clearing this bit while DSI is in use is a known issue and intel_dsi_pre_enable() / intel_dsi_post_disable() already set / clear it as appropriate. This commit modifies vlv_init_display_clock_gating() to leave the DPOUNIT_CLOCK_GATE_DISABLE bit alone fixing PIPE-A getting stuck. BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=97330 Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> --- drivers/gpu/drm/i915/intel_runtime_pm.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c index 356c662..b5ce7cb 100644 --- a/drivers/gpu/drm/i915/intel_runtime_pm.c +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c @@ -1039,7 +1039,18 @@ static bool vlv_power_well_enabled(struct drm_i915_private *dev_priv, static void vlv_init_display_clock_gating(struct drm_i915_private *dev_priv) { - I915_WRITE(DSPCLK_GATE_D, VRHUNIT_CLOCK_GATE_DISABLE); + u32 val; + + /* + * When on driver load, PIPE A may be active and driving a DSI display. + * Preserve DPOUNIT_CLOCK_GATE_DISABLE to avoid PIPE A getting stuck + * (and never recovering) in this case. intel_dsi_post_disable() will + * clear it when we turn off the display. + */ + val = I915_READ(DSPCLK_GATE_D); + val &= DPOUNIT_CLOCK_GATE_DISABLE; + val |= VRHUNIT_CLOCK_GATE_DISABLE; + I915_WRITE(DSPCLK_GATE_D, val); /* * Disable trickle feed and enable pnd deadline calculation -- 2.9.3 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
