On Mon, Jul 14, 2025 at 21:51, Rob Clark <rob.cl...@oss.qualcomm.com> wrote:
>
> On Mon, Jul 14, 2025 at 10:36 AM Dale Whinham <dal...@gmail.com> wrote:
> >
> > From: Jérôme de Bretagne <jerome.debreta...@gmail.com>
> >
> > The OLED display in the Surface Pro 11 reports a maximum link rate of
> > zero in its DPCD, causing it to fail to probe correctly.
> >
> > The Surface Pro 11's DSDT table contains some XML with an
> > "EDPOverrideDPCDCaps" block that defines the max link rate as 0x1E
> > (8.1Gbps/HBR3).
> >
> > Add a quirk to conditionally override the max link rate if its value
> > is zero specifically for this model.
> >
> > Signed-off-by: Jérôme de Bretagne <jerome.debreta...@gmail.com>
> > Signed-off-by: Dale Whinham <dal...@gmail.com>
> > ---
> > drivers/gpu/drm/msm/dp/dp_panel.c | 13 +++++++++++++
> > 1 file changed, 13 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c
> > b/drivers/gpu/drm/msm/dp/dp_panel.c
> > index 4e8ab75c771b..b2e65b987c05 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_panel.c
> > +++ b/drivers/gpu/drm/msm/dp/dp_panel.c
> > @@ -11,6 +11,8 @@
> > #include <drm/drm_of.h>
> > #include <drm/drm_print.h>
> >
> > +#include <linux/dmi.h>
> > +
> > #define DP_MAX_NUM_DP_LANES 4
> > #define DP_LINK_RATE_HBR2 540000 /* kbytes */
> >
> > @@ -58,6 +60,17 @@ static int msm_dp_panel_read_dpcd(struct msm_dp_panel
> > *msm_dp_panel)
> > if (rc)
> > return rc;
> >
> > + /*
> > + * for some reason the ATNA30DW01-1 OLED panel in the Surface Pro 11
> > + * reports a max link rate of 0 in the DPCD. Fix it to match the
> > + * EDPOverrideDPCDCaps string found in the ACPI DSDT
> > + */
> > + if (dpcd[DP_MAX_LINK_RATE] == 0 &&
> > + dmi_match(DMI_SYS_VENDOR, "Microsoft Corporation") &&
> > + dmi_match(DMI_PRODUCT_NAME, "Microsoft Surface Pro, 11th
> > Edition")) {
> > + dpcd[1] = DP_LINK_BW_8_1;
> > + }
>
> Not a dp expert myself, but..
>
> In drm_dp_helpers.c there is dpcd_quirk_list[].. which applies quirks
> based on the oui ("Organizational Unique ID") of the dp sink. I think
> this would be the correct way to handle this. Although I guess you'll
> need to add a new quirk for this.
>
> Idk if the surface pro 11 has multiple different panel options. If so
> you defn wouldn't want to match on the DMI.
>
> BR,
> -R
Thanks Rob for the feedback, I have a working implementation
based on your suggestion with a new quirk, we will switch to it in V2.
Best,
Jérôme
> > +
> > msm_dp_panel->vsc_sdp_supported =
> > drm_dp_vsc_sdp_supported(panel->aux, dpcd);
> > link_info = &msm_dp_panel->link_info;
> > link_info->revision = dpcd[DP_DPCD_REV];
> > --
> > 2.50.1
> >
