> -----Original Message-----
> From: Deak, Imre <imre.deak@xxxxxxxxx>
> Sent: Wednesday, July 24, 2024 4:57 PM
> To: Kandpal, Suraj <suraj.kandpal@xxxxxxxxx>
> Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH 09/14] drm/i915/dp_mst: Reduce the link parameters in
> BW order after LT failures
>
> On Wed, Jul 24, 2024 at 09:43:55AM +0300, Kandpal, Suraj wrote:
> >
> >
> > > -----Original Message-----
> > > From: Intel-gfx <intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf
> > > Of Imre Deak
> > > Sent: Monday, July 22, 2024 10:25 PM
> > > To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > > Subject: [PATCH 09/14] drm/i915/dp_mst: Reduce the link parameters
> > > in BW order after LT failures
> > >
> > > On MST links - at least for some MST branch devices - the list of
> > > modes returned to users on an enabled link depends on the current
> > > link rate/lane count parameters (besides the DPRX link capabilities,
> > > any MST branch BW limit and the maximum link parameters reduced
> > > after LT failures). In particular the MST branch BW limit may depend
> > > on the link rate/lane count parameters programmed to DPCD. After an
> > > LT failure and limiting the maximum link parameters accordingly,
> > > users should see a mode list reflecting these new limits. However
> > > with the current fallback order this isn't ensured, as the new limit
> > > could allow for modes requiring a higher link BW, but these modes will
> be filtered out due to the enabled link's lower link BW.
> > >
> > > Ensure that the mode list changes in a consistent way after a link
> > > training failure and reducing the link parameters by changing the
> > > fallback order on MST links to happen in BW order.
> > >
> > > Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
> > > ---
> > > .../drm/i915/display/intel_display_types.h | 12 ++
> > > drivers/gpu/drm/i915/display/intel_dp.c | 111 ++++++++++++++++++
> > > drivers/gpu/drm/i915/display/intel_dp.h | 2 +
> > > .../drm/i915/display/intel_dp_link_training.c | 43 ++++++-
> > > 4 files changed, 166 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h
> > > b/drivers/gpu/drm/i915/display/intel_display_types.h
> > > index 3501125c55158..51e2151315977 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> > > +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> > > @@ -1778,6 +1778,18 @@ struct intel_dp {
> > > int common_rates[DP_MAX_SUPPORTED_RATES];
> > > struct {
> > > /* TODO: move the rest of link specific fields to here
> > > */
> > > + /* common rate,lane_count configs in bw order */
> > > + int num_configs;
> > > +#define INTEL_DP_MAX_LANE_COUNT 4
> > > +#define INTEL_DP_MAX_SUPPORTED_LANE_COUNTS
> > > (ilog2(INTEL_DP_MAX_LANE_COUNT) + 1)
> >
> > I feel this name could be a little confusing this define here I am
> > assuming the Different lane count configs we can support which would
> > be 1,2,4 hence 3, Maybe renaming it as DP_MAX_LANE_COUNT_CONFIG
>
> Ok, will rename it to INTEL_DP_MAX_SUPPORTED_LANE_CONFIGS.
>
> > > +#define INTEL_DP_LANE_COUNT_EXP_BITS
> > > order_base_2(INTEL_DP_MAX_SUPPORTED_LANE_COUNTS)
> > > +#define INTEL_DP_LINK_RATE_IDX_BITS (BITS_PER_TYPE(u8) -
> > > INTEL_DP_LANE_COUNT_EXP_BITS)
> > > +#define INTEL_DP_MAX_LINK_CONFIGS
> > > (DP_MAX_SUPPORTED_RATES * \
> > > +
> > > INTEL_DP_MAX_SUPPORTED_LANE_COUNTS)
> > > + struct intel_dp_link_config {
> > > + u8 link_rate_idx:INTEL_DP_LINK_RATE_IDX_BITS;
> > > + u8
> > > lane_count_exp:INTEL_DP_LANE_COUNT_EXP_BITS;
> > > + } configs[INTEL_DP_MAX_LINK_CONFIGS];
> > > /* Max lane count for the current link */
> > > int max_lane_count;
> > > /* Max rate for the current link */ diff --git
> > > a/drivers/gpu/drm/i915/display/intel_dp.c
> > > b/drivers/gpu/drm/i915/display/intel_dp.c
> > > index 0882dddd97206..d3529c5836393 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > > @@ -29,6 +29,7 @@
> > > #include <linux/i2c.h>
> > > #include <linux/notifier.h>
> > > #include <linux/slab.h>
> > > +#include <linux/sort.h>
> > > #include <linux/string_helpers.h>
> > > #include <linux/timekeeping.h>
> > > #include <linux/types.h>
> > > @@ -634,6 +635,114 @@ int intel_dp_rate_index(const int *rates, int
> > > len, int rate)
> > > return -1;
> > > }
> > >
> > > +static int intel_dp_link_config_rate(struct intel_dp *intel_dp,
> > > + const struct intel_dp_link_config *lc) {
> > > + return intel_dp_common_rate(intel_dp, lc->link_rate_idx); }
> > > +
> > > +static int intel_dp_link_config_lane_count(const struct
> > > +intel_dp_link_config *lc) {
> > > + return 1 << lc->lane_count_exp; }
> > > +
> > > +static int intel_dp_link_config_bw(struct intel_dp *intel_dp,
> > > + const struct intel_dp_link_config *lc) {
> > > + return
> > > drm_dp_max_dprx_data_rate(intel_dp_link_config_rate(intel_dp, lc),
> > > +
> > > +intel_dp_link_config_lane_count(lc));
> > > +}
> > > +
> > > +static int link_config_cmp_by_bw(const void *a, const void *b,
> > > +const void *p) {
> > > + struct intel_dp *intel_dp = (struct intel_dp *)p; /* remove const
> */
> > > + const struct intel_dp_link_config *lc_a = a;
> > > + const struct intel_dp_link_config *lc_b = b;
> > > + int bw_a = intel_dp_link_config_bw(intel_dp, lc_a);
> > > + int bw_b = intel_dp_link_config_bw(intel_dp, lc_b);
> > > +
> > > + if (bw_a != bw_b)
> > > + return bw_a - bw_b;
> > > +
> > > + return intel_dp_link_config_rate(intel_dp, lc_a) -
> > > + intel_dp_link_config_rate(intel_dp, lc_b); }
> > > +
> > > +static void link_config_swap(void *a, void *b, int size, const void
> > > +* __always_unused p) {
> > > + struct intel_dp_link_config *lc_a = a;
> > > + struct intel_dp_link_config *lc_b = b;
> > > +
> > > + swap(*lc_a, *lc_b);
> > > +}
> > > +
> > > +static void intel_dp_link_config_init(struct intel_dp *intel_dp) {
> > > + struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > + struct intel_dp_link_config *lc;
> > > + int num_common_lane_counts;
> > > + int i;
> > > + int j;
> > > +
> > > + if (drm_WARN_ON(&i915->drm,
> > > !is_power_of_2(intel_dp_max_common_lane_count(intel_dp))))
> > > + return;
> > > +
> > > + num_common_lane_counts =
> > > +ilog2(intel_dp_max_common_lane_count(intel_dp)) + 1;
> >
> > Same thing here can we rename it as num_common_lane_count_config
>
> Ok, will rename to num_common_lane_configs.
>
Rest LGTM,
Reviewed-by: Suraj Kandpal <suraj.kandpal@xxxxxxxxx>
> > Regards,
> > Suraj Kandpal
> > > +
> > > + if (drm_WARN_ON(&i915->drm, intel_dp->num_common_rates *
> > > num_common_lane_counts >
> > > + ARRAY_SIZE(intel_dp->link.configs)))
> > > + return;
> > > +
> > > + intel_dp->link.num_configs = intel_dp->num_common_rates *
> > > +num_common_lane_counts;
> > > +
> > > + lc = &intel_dp->link.configs[0];
> > > + for (i = 0; i < intel_dp->num_common_rates; i++) {
> > > + for (j = 0; j < num_common_lane_counts; j++) {
> > > + lc->lane_count_exp = j;
> > > + lc->link_rate_idx = i;
> > > +
> > > + lc++;
> > > + }
> > > + }
> > > +
> > > + sort_r(intel_dp->link.configs, intel_dp->link.num_configs,
> > > + sizeof(intel_dp->link.configs[0]),
> > > + link_config_cmp_by_bw, link_config_swap,
> > > + intel_dp);
> > > +}
> > > +
> > > +void intel_dp_link_config_get(struct intel_dp *intel_dp, int idx,
> > > +int *link_rate, int *lane_count) {
> > > + struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > + const struct intel_dp_link_config *lc;
> > > +
> > > + if (drm_WARN_ON(&i915->drm, idx < 0 || idx >= intel_dp-
> > > >link.num_configs))
> > > + idx = 0;
> > > +
> > > + lc = &intel_dp->link.configs[idx];
> > > +
> > > + *link_rate = intel_dp_link_config_rate(intel_dp, lc);
> > > + *lane_count = intel_dp_link_config_lane_count(lc);
> > > +}
> > > +
> > > +int intel_dp_link_config_index(struct intel_dp *intel_dp, int
> > > +link_rate, int lane_count) {
> > > + int link_rate_idx =
> > > +intel_dp_rate_index(intel_dp->common_rates,
> > > intel_dp->num_common_rates,
> > > + link_rate);
> > > + int lane_count_exp = ilog2(lane_count);
> > > + int i;
> > > +
> > > + for (i = 0; i < intel_dp->link.num_configs; i++) {
> > > + const struct intel_dp_link_config *lc = &intel_dp-
> > > >link.configs[i];
> > > +
> > > + if (lc->lane_count_exp == lane_count_exp &&
> > > + lc->link_rate_idx == link_rate_idx)
> > > + return i;
> > > + }
> > > +
> > > + return -1;
> > > +}
> > > +
> > > static void intel_dp_set_common_rates(struct intel_dp *intel_dp) {
> > > struct drm_i915_private *i915 = dp_to_i915(intel_dp); @@
> > > -652,6
> > > +761,8 @@ static void intel_dp_set_common_rates(struct intel_dp
> > > *intel_dp)
> > > intel_dp->common_rates[0] = 162000;
> > > intel_dp->num_common_rates = 1;
> > > }
> > > +
> > > + intel_dp_link_config_init(intel_dp);
> > > }
> > >
> > > static bool intel_dp_link_params_valid(struct intel_dp *intel_dp,
> > > int link_rate, diff --git a/drivers/gpu/drm/i915/display/intel_dp.h
> > > b/drivers/gpu/drm/i915/display/intel_dp.h
> > > index 9be539edf817b..1b9aaddd8c35c 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_dp.h
> > > +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> > > @@ -107,6 +107,8 @@ int intel_dp_max_common_rate(struct intel_dp
> > > *intel_dp); int intel_dp_max_common_lane_count(struct intel_dp
> > > *intel_dp); int intel_dp_common_rate(struct intel_dp *intel_dp, int
> > > index); int intel_dp_rate_index(const int *rates, int len, int
> > > rate);
> > > +int intel_dp_link_config_index(struct intel_dp *intel_dp, int
> > > +link_rate, int lane_count); void intel_dp_link_config_get(struct
> > > +intel_dp *intel_dp, int idx, int *link_rate, int *lane_count);
> > > void intel_dp_update_sink_caps(struct intel_dp *intel_dp); void
> > > intel_dp_reset_link_params(struct intel_dp *intel_dp);
> > >
> > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> > > b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> > > index 214c8858b8a94..0c8e0d6437b5b 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> > > @@ -1170,6 +1170,41 @@ static bool
> > > intel_dp_can_link_train_fallback_for_edp(struct intel_dp *intel_dp,
> > > return true;
> > > }
> > >
> > > +static bool reduce_link_params_in_bw_order(struct intel_dp *intel_dp,
> > > + const struct
> > > +intel_crtc_state
> > > *crtc_state,
> > > + int *new_link_rate, int
> > > *new_lane_count) {
> > > + int link_rate;
> > > + int lane_count;
> > > + int i;
> > > +
> > > + i = intel_dp_link_config_index(intel_dp,
> > > + crtc_state->port_clock,
> > > crtc_state->lane_count);
> > > + for (i--; i >= 0; i--) {
> > > + intel_dp_link_config_get(intel_dp, i, &link_rate,
> > > &lane_count);
> > > +
> > > + if ((intel_dp->link.force_rate &&
> > > + intel_dp->link.force_rate != link_rate) ||
> > > + (intel_dp->link.force_lane_count &&
> > > + intel_dp->link.force_lane_count != lane_count))
> > > + continue;
> > > +
> > > + /* TODO: Make switching from UHBR to non-UHBR rates
> > > work. */
> > > + if (drm_dp_is_uhbr_rate(crtc_state->port_clock) !=
> > > + drm_dp_is_uhbr_rate(link_rate))
> > > + continue;
> > > +
> > > + break;
> > > + }
> > > +
> > > + if (i < 0)
> > > + return false;
> > > +
> > > + *new_link_rate = link_rate;
> > > + *new_lane_count = lane_count;
> > > +
> > > + return true;
> > > +}
> > > +
> > > static int reduce_link_rate(struct intel_dp *intel_dp, int current_rate) {
> > > int rate_index;
> > > @@ -1231,8 +1266,12 @@ static bool
> > > reduce_link_params_in_rate_lane_order(struct intel_dp *intel_dp,
> > > static bool reduce_link_params(struct intel_dp *intel_dp, const
> > > struct intel_crtc_state *crtc_state,
> > > int *new_link_rate, int *new_lane_count) {
> > > - return reduce_link_params_in_rate_lane_order(intel_dp, crtc_state,
> > > - new_link_rate,
> > > new_lane_count);
> > > + if (intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DP_MST))
> > > + return reduce_link_params_in_bw_order(intel_dp,
> > > crtc_state,
> > > + new_link_rate,
> > > new_lane_count);
> > > + else
> > > + return reduce_link_params_in_rate_lane_order(intel_dp,
> > > crtc_state,
> > > +
> > > + new_link_rate,
> > > new_lane_count);
> > > }
> > >
> > > static int intel_dp_get_link_train_fallback_values(struct intel_dp
> > > *intel_dp,
> > > --
> > > 2.44.2
> >
