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drm/i915/bxt: backlight clock gating workaround

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Per bspec, "Backlight PWM may stop in the asserted state, causing
backlight to stay fully on. WA: Before disabling PWM, set CLKGATE_DIS_0
0x46530 bit 13 PWM1 Gating Dis (for PWM1) or bit 14 PWM2 Gating Dis (for
PWM2). The bits can remain set without harm." (There's no workaround
name for this.)

This fixes some Broxton backlight issues.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
[Jani: cleanup & commit message]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1448958232-26520-3-git-send-email-jani.nikula@intel.com
This commit is contained in:
Imre Deak
2015-12-01 10:23:52 +02:00
committed by Jani Nikula
parent 5075222b04
commit d965e7ac7a
2 changed files with 15 additions and 0 deletions
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8
drivers/gpu/drm/i915/intel_pm.c
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@@ -66,6 +66,14 @@ static void bxt_init_clock_gating(struct drm_device *dev)
*/
I915_WRITE(GEN8_UCGCTL6, I915_READ(GEN8_UCGCTL6) |
GEN8_HDCUNIT_CLOCK_GATE_DISABLE_HDCREQ);
/*
* Wa: Backlight PWM may stop in the asserted state, causing backlight
* to stay fully on.
*/
if (IS_BXT_REVID(dev_priv, BXT_REVID_B0, REVID_FOREVER))
I915_WRITE(GEN9_CLKGATE_DIS_0, I915_READ(GEN9_CLKGATE_DIS_0) |
PWM1_GATING_DIS | PWM2_GATING_DIS);
}
static void i915_pineview_get_mem_freq(struct drm_device *dev)