Definitely a TODO there that I no longer can remember why I didn't just do
this in the first place, lol. Thank you for the fix
Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx>
On Fri, 2023-09-29 at 18:49 +0300, Imre Deak wrote:
> Atm the MST encoder config computation may use an out-of-date pbn_div
> value, if the sink is unplugged and a sink is replugged with different
> link rate/lane count capabilities. The current way of reinitializing
> pbn_div depends on pbn_div getting cleared via intel_atomic_check() ->
> drm_dp_mst_atomic_check() ->
> drm_dp_mst_atomic_check_payload_alloc_limits(), however the clearing
> won't happen if the sink got unplugged (and hence
> drm_dp_mst_topology_mgr::mst_state being false).
>
> To fix the above, simply update pbn_div unconditionally during config
> computation, making pbn_div always match the link rate and lane count.
>
> Cc: Lyude Paul <lyude@xxxxxxxxxx>
> Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_dp_mst.c | 9 +++------
> 1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 648cf37e02a87..42ddfc85d72d6 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -94,12 +94,9 @@ static int intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
> crtc_state->lane_count = limits->max_lane_count;
> crtc_state->port_clock = limits->max_rate;
>
> - // TODO: Handle pbn_div changes by adding a new MST helper
> - if (!mst_state->pbn_div) {
> - mst_state->pbn_div = drm_dp_get_vc_payload_bw(&intel_dp->mst_mgr,
> - crtc_state->port_clock,
> - crtc_state->lane_count);
> - }
> + mst_state->pbn_div = drm_dp_get_vc_payload_bw(&intel_dp->mst_mgr,
> + crtc_state->port_clock,
> + crtc_state->lane_count);
>
> for (bpp = max_bpp; bpp >= min_bpp; bpp -= step) {
> drm_dbg_kms(&i915->drm, "Trying bpp %d\n", bpp);
--
Cheers,
Lyude Paul (she/her)
Software Engineer at Red Hat
