On Fri, 2021-04-30 at 17:22 -0400, Nikola Cornij wrote:

[why] Previously used value was not safe to provide the correct value, i.e. it could be 0 if not not configured, leading to no MST on this platform.

[how] Do not use the value from BIOS, but from the structure populated at encoder initialization time.

Fixes: 98025a62cb00 ("drm/dp_mst: Use Extended Base Receiver Capability DPCD space") Signed-off-by: Nikola Cornij nikola.cornij@amd.com

---

drivers/gpu/drm/i915/display/intel_dp_mst.c | 5 ++---  1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c index bf7f8487945c..01a0ed99988f 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c @@ -942,7 +942,6 @@ intel_dp_mst_encoder_init(struct intel_digital_port *dig_port, int conn_base_id)         struct intel_dp *intel_dp = &dig_port->dp;         enum port port = dig_port->base.port;         int ret; -       int bios_max_link_rate;           if (!HAS_DP_MST(i915) || intel_dp_is_edp(intel_dp))                 return 0; @@ -957,11 +956,11 @@ intel_dp_mst_encoder_init(struct intel_digital_port *dig_port, int conn_base_id)           /* create encoders */         intel_dp_create_fake_mst_encoders(dig_port); -       bios_max_link_rate = intel_bios_dp_max_link_rate(&dig_port->base);         ret = drm_dp_mst_topology_mgr_init(&intel_dp->mst_mgr, &i915->drm,                                            &intel_dp->aux, 16, 3,                                            (u8)dig_port->max_lanes, -                                          (u8)(bios_max_link_rate / 27000), conn_base_id); +                                          (u8)(intel_dp-

...

source_rates[intel_dp->num_source_rates - 1] / 27000),

+                                          conn_base_id);

This line is kind of long, I'd say we should just store the max link rate in a local variable like max_link_rate, then just pass that to drm_dp_mst_topology_mgr_init()

Also, the commit message should probably be:

drm/i915: Use the correct max source link rate for MST

With those two things fixed:

Reviewed-by: Lyude Paul lyude@redhat.com

if (ret)                 return ret;