> -----Original Message-----
> From: Almahallawy, Khaled <khaled.almahallawy@xxxxxxxxx>
> Sent: Wednesday, February 7, 2024 4:11 AM
> To: Murthy, Arun R <arun.r.murthy@xxxxxxxxx>; intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: Shankar, Uma <uma.shankar@xxxxxxxxx>; Nikula, Jani
> <jani.nikula@xxxxxxxxx>; Deak, Imre <imre.deak@xxxxxxxxx>; Syrjala, Ville
> <ville.syrjala@xxxxxxxxx>
> Subject: Re: [RFC 1/4] drm/i915/display/dp: Add DP fallback on LT
>
> On Tue, 2024-02-06 at 16:17 +0530, Arun R Murthy wrote:
> > Fallback mandates on DP link training failure. This patch just covers
> > the DP2.0 fallback sequence.
> >
> > TODO: Need to implement the DP1.4 fallback.
> >
> > Signed-off-by: Arun R Murthy <arun.r.murthy@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/display/intel_dp.c | 92 ++++++++++++++++++++++-
> > --
> > 1 file changed, 82 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> > b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 10ec231acd98..82d354a6b0cd 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -104,6 +104,50 @@ static const u8 valid_dsc_bpp[] = {6, 8, 10, 12,
> > 15};
> > */
> > static const u8 valid_dsc_slicecount[] = {1, 2, 4};
> >
> > +/* DL Link Rates */
> > +#define UHBR20 2000000
> > +#define UHBR13P5 1350000
>
> Do we have 13.5G support?
> Plz check Specs:55726 Note 6
>
Long back had posted a patch to remove UHBR13.5(https://patchwork.freedesktop.org/series/119555/), but was rejected. Hence added this.
Thanks and Regards,
Arun R Murthy
--------------------
> Thanks
> Khaled
>
> > +#define UHBR10 1000000
> > +#define HBR3 810000
> > +#define HBR2 540000
> > +#define HBR 270000
> > +#define RBR 162000
> > +
> > +/* DP Lane Count */
> > +#define LANE_COUNT_4 4
> > +#define LANE_COUNT_2 2
> > +#define LANE_COUNT_1 1
> > +
> > +/* DP2.0 fallback values */
> > +struct dp_fallback {
> > + u32 link_rate;
> > + u8 lane_count;
> > +};
> > +
> > +struct dp_fallback dp2dot0_fallback[] = {
> > + {UHBR20, LANE_COUNT_4},
> > + {UHBR13P5, LANE_COUNT_4},
> > + {UHBR20, LANE_COUNT_2},
> > + {UHBR10, LANE_COUNT_4},
> > + {UHBR13P5, LANE_COUNT_2},
> > + {HBR3, LANE_COUNT_4},
> > + {UHBR20, LANE_COUNT_1},
> > + {UHBR10, LANE_COUNT_2},
> > + {HBR2, LANE_COUNT_4},
> > + {UHBR13P5, LANE_COUNT_1},
> > + {HBR3, LANE_COUNT_2},
> > + {UHBR10, LANE_COUNT_1},
> > + {HBR2, LANE_COUNT_2},
> > + {HBR, LANE_COUNT_4},
> > + {HBR3, LANE_COUNT_1},
> > + {RBR, LANE_COUNT_4},
> > + {HBR2, LANE_COUNT_1},
> > + {HBR, LANE_COUNT_2},
> > + {RBR, LANE_COUNT_2},
> > + {HBR, LANE_COUNT_1},
> > + {RBR, LANE_COUNT_1},
> > +};
> > +
> > /**
> > * intel_dp_is_edp - is the given port attached to an eDP panel
> > (either CPU or PCH)
> > * @intel_dp: DP struct
> > @@ -299,6 +343,19 @@ static int intel_dp_common_len_rate_limit(const
> > struct intel_dp *intel_dp,
> > intel_dp->num_common_rates, max_rate);
> }
> >
> > +static bool intel_dp_link_rate_supported(struct intel_dp *intel_dp,
> > u32 link_rate)
> > +{
> > + u8 i;
> > +
> > + for (i = 0; i < ARRAY_SIZE(intel_dp->common_rates); i++) {
> > + if (intel_dp->common_rates[i] == link_rate)
> > + return true;
> > + else
> > + continue;
> > + }
> > + return false;
> > +}
> > +
> > static int intel_dp_common_rate(struct intel_dp *intel_dp, int
> > index)
> > {
> > if (drm_WARN_ON(&dp_to_i915(intel_dp)->drm,
> > @@ -671,15 +728,6 @@ int
> > intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> > struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > int index;
> >
> > - /*
> > - * TODO: Enable fallback on MST links once MST link compute can
> > handle
> > - * the fallback params.
> > - */
> > - if (intel_dp->is_mst) {
> > - drm_err(&i915->drm, "Link Training Unsuccessful\n");
> > - return -1;
> > - }
> > -
> > if (intel_dp_is_edp(intel_dp) && !intel_dp->use_max_params) {
> > drm_dbg_kms(&i915->drm,
> > "Retrying Link training for eDP with max
> parameters\n"); @@
> > -687,6 +735,31 @@ int intel_dp_get_link_train_fallback_values(struct
> > intel_dp *intel_dp,
> > return 0;
> > }
> >
> > + /* DP fallback values */
> > + if (intel_dp->dpcd[DP_MAIN_LINK_CHANNEL_CODING] &
> > DP_CAP_ANSI_128B132B) {
> > + for(index = 0; index < ARRAY_SIZE(dp2dot0_fallback);
> > index++) {
> > + if (link_rate ==
> > dp2dot0_fallback[index].link_rate &&
> > + lane_count ==
> > dp2dot0_fallback[index].lane_count) {
> > + for(index += 1; index <
> > ARRAY_SIZE(dp2dot0_fallback); index++) {
> > + if
> > (intel_dp_link_rate_supported(intel_dp,
> > + dp2dot0_fallbac
> > k[index].link_rate)) {
> > + intel_dp_set_link_param
> > s(intel_dp,
> > + d
> > p2dot0_fallback[index].link_rate,
> > + d
> > p2dot0_fallback[index].lane_count);
> > + drm_dbg_kms(&i915->drm,
> > + "Retrying
> > Link training with link rate %d and lane count %d\n",
> > + dp2dot0_fal
> > lback[index].link_rate,
> > + dp2dot0_fal
> > lback[index].lane_count);
> > + return 0;
> > + }
> > + }
> > + }
> > + }
> > + /* Report failure and fail link training */
> > + drm_err(&i915->drm, "Link Training Unsuccessful\n");
> > + return -1;
> > + }
> > +
> > index = intel_dp_rate_index(intel_dp->common_rates,
> > intel_dp->num_common_rates,
> > link_rate);
> > @@ -716,7 +789,6 @@ int
> > intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
> > drm_err(&i915->drm, "Link Training Unsuccessful\n");
> > return -1;
> > }
> > -
> > return 0;
> > }
> >
