From 484956e48cc60ddc9a8ca32223a791c026d1e662 Mon Sep 17 00:00:00 2001
From: Lyude Paul <lyude@redhat.com>
Date: Tue, 11 Feb 2020 13:33:48 -0500
Subject: drm/i915: Force DPCD backlight mode for some Dell CML 2020 panels
Git-commit: ba518bbd3f3c265419fa8c3702940cb7c642c6a5
Patch-mainline: v5.7-rc1
References: jsc#SLE-12680, jsc#SLE-12880, jsc#SLE-12882, jsc#SLE-12883, jsc#SLE-13496, jsc#SLE-15322
According to Dell, trying to match their panels via OUI is not reliable
enough and we've been told that we should check against the EDID
instead. As well, Dell seems to have some panels that are actually
intended to switch between using PWM for backlight controls and DPCD for
backlight controls depending on whether or not the panel is in HDR or
SDR mode. Yikes.
Regardless, we need to add quirks for these so that DPCD backlight
controls get enabled by default, since without additional driver support
that's the only form of brightness control that will work. Hopefully in
the future we can remove these quirks once we have a better way of
probing for this.
Changes since v1:
* Add one more EDID per Dell's request
* Remove model number (which is possibly wrong) and replace with Dell
CML 2020 systems
Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200211183358.157448-4-lyude@redhat.com
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/drm_dp_helper.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 671f4d3968fc..c6fbe6e6bc9d 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -1299,6 +1299,20 @@ static const struct edid_quirk edid_quirk_list[] = {
* only supports DPCD backlight controls
*/
{ MFG(0x4c, 0x83), PROD_ID(0x41, 0x41), BIT(DP_QUIRK_FORCE_DPCD_BACKLIGHT) },
+ /*
+ * Some Dell CML 2020 systems have panels support both AUX and PWM
+ * backlight control, and some only support AUX backlight control. All
+ * said panels start up in AUX mode by default, and we don't have any
+ * support for disabling HDR mode on these panels which would be
+ * required to switch to PWM backlight control mode (plus, I'm not
+ * even sure we want PWM backlight controls over DPCD backlight
+ * controls anyway...). Until we have a better way of detecting these,
+ * force DPCD backlight mode on all of them.
+ */
+ { MFG(0x06, 0xaf), PROD_ID(0x9b, 0x32), BIT(DP_QUIRK_FORCE_DPCD_BACKLIGHT) },
+ { MFG(0x06, 0xaf), PROD_ID(0xeb, 0x41), BIT(DP_QUIRK_FORCE_DPCD_BACKLIGHT) },
+ { MFG(0x4d, 0x10), PROD_ID(0xc7, 0x14), BIT(DP_QUIRK_FORCE_DPCD_BACKLIGHT) },
+ { MFG(0x4d, 0x10), PROD_ID(0xe6, 0x14), BIT(DP_QUIRK_FORCE_DPCD_BACKLIGHT) },
};
#undef MFG
--
2.28.0