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
> +
> 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
>
