From: Shawn Lee <shawn.c.lee@xxxxxxxxx> Backlight enable is supposed to do a full setup of the backlight. We were missing the PWM alternate increment bit in the south chicken registers on lpt+ pch. This potentially caused a PWM frequency change when the chicken register value was lost e.g. on suspend. v2 by Jani, rebase on the patch caching alt increment Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97486 Cc: Cooper Chiou <cooper.chiou@xxxxxxxxx> Cc: Wei Shun Chen <wei.shun.chang@xxxxxxxxx> Cc: Gary C Wang <gary.c.wang@xxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Shawn Lee <shawn.c.lee@xxxxxxxxx> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> --- drivers/gpu/drm/i915/intel_panel.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c index 8bc43205d6a0..be4b4d546fd9 100644 --- a/drivers/gpu/drm/i915/intel_panel.c +++ b/drivers/gpu/drm/i915/intel_panel.c @@ -841,7 +841,7 @@ static void lpt_enable_backlight(struct intel_connector *connector) { struct drm_i915_private *dev_priv = to_i915(connector->base.dev); struct intel_panel *panel = &connector->panel; - u32 pch_ctl1, pch_ctl2; + u32 pch_ctl1, pch_ctl2, schicken; pch_ctl1 = I915_READ(BLC_PWM_PCH_CTL1); if (pch_ctl1 & BLM_PCH_PWM_ENABLE) { @@ -850,6 +850,22 @@ static void lpt_enable_backlight(struct intel_connector *connector) I915_WRITE(BLC_PWM_PCH_CTL1, pch_ctl1); } + if (HAS_PCH_LPT(dev_priv)) { + schicken = I915_READ(SOUTH_CHICKEN2); + if (panel->backlight.alternate_pwm_increment) + schicken |= LPT_PWM_GRANULARITY; + else + schicken &= ~LPT_PWM_GRANULARITY; + I915_WRITE(SOUTH_CHICKEN2, schicken); + } else { + schicken = I915_READ(SOUTH_CHICKEN1); + if (panel->backlight.alternate_pwm_increment) + schicken |= SPT_PWM_GRANULARITY; + else + schicken &= ~SPT_PWM_GRANULARITY; + I915_WRITE(SOUTH_CHICKEN1, schicken); + } + pch_ctl2 = panel->backlight.max << 16; I915_WRITE(BLC_PWM_PCH_CTL2, pch_ctl2); -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html