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Date:   Fri, 17 Feb 2017 12:48:47 +0800
From:   River Zhou <>
To:     Greg Kroah-Hartman <>
Cc:     Daniel Vetter <>,
        Jani Nikula <>,
        David Airlie <>,,,, River Zhou <>
Subject: [PATCH] backport commit bb98e72adaf9d19719aba35f802d4836f5d5176c to 4.4.49 fixed i915 dsi init bug passed test on my Lenovo Miix 2 8 (Bay Trail Z3740)

commit bb98e72adaf9d19719aba35f802d4836f5d5176c
Author: Hans de Goede <>
Date:   Fri Dec 2 15:29:04 2016 +0100

    drm/i915/dsi: Do not clear DPOUNIT_CLOCK_GATE_DISABLE from vlv_init_display_clock_gating

    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 a pipe 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 the pipe getting stuck.

    Changes in v2:
    -Replace PIPE-A with "a pipe" or "the pipe" in the commit msg and

    Signed-off-by: Hans de Goede <>
    Reviewed-by: Ville Syrjälä <>
    Signed-off-by: Ville Syrjälä <>
    (cherry picked from commit 721d484563e1a51ada760089c490cbc47e909756)
    Signed-off-by: Jani Nikula <>

Signed-off-by: River Zhou <>
 drivers/gpu/drm/i915/intel_pm.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 3f80216..e7c1851 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -6803,7 +6803,18 @@ static void ivybridge_init_clock_gating(struct drm_device *dev)
 static void vlv_init_display_clock_gating(struct drm_i915_private *dev_priv)
+        u32 val;
+        /*
+        * On driver load, a pipe may be active and driving a DSI display.
+        * Preserve DPOUNIT_CLOCK_GATE_DISABLE to avoid the pipe 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);
+        I915_WRITE(DSPCLK_GATE_D, val);
 	 * Disable trickle feed and enable pnd deadline calculation

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