On Thu, May 11, 2020, Ville Syrjälä wrote: >On Thu, May 07, 2020 at 06:46:17PM -0400, Lyude Paul wrote: >> On Thu, 2020-04-30 at 02:37 +0000, Lee, Shawn C wrote: >> > On Sat, 2020-04-25, Lyude Paul wrote: >> > > Hi! Sorry this took me a little while to get back to, I had a couple of >> > > MST regressions that I had to look into >> > > >> > > On Sat, 2020-04-18 at 05:24 +0800, Lee Shawn C wrote: >> > > > So far, max dot clock rate for MST mode rely on physcial bandwidth >> > > > limitation. It would caused compatibility issue if source display >> > > > resolution exceed MST hub output ability. >> > > > >> > > > For example, source DUT had DP 1.2 output capability. >> > > > And MST docking just support HDMI 1.4 spec. When a HDMI 2.0 monitor >> > > > connected. Source would retrieve EDID from external and get max >> > > > resolution 4k@60fps. DP 1.2 can support 4K@60fps because it did not >> > > > surpass DP physical bandwidth limitation. >> > > > Do modeset to 4k@60fps, source output display data but MST docking >> > > > can't output HDMI properly due to this resolution already over HDMI >> > > > 1.4 spec. >> > > > >> > > > Refer to commit <fcf463807596> ("drm/dp_mst: Use full_pbn instead of >> > > > available_pbn for bandwidth checks"). >> > > > Source driver should refer to full_pbn to evaluate sink output >> > > > capability. And filter out the resolution surpass sink output >> > > > limitation. >> > > > >> > > > Cc: Manasi Navare <manasi.d.navare@xxxxxxxxx> >> > > > Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> >> > > > Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx> >> > > > Cc: Cooper Chiou <cooper.chiou@xxxxxxxxx> >> > > > Cc: Lyude Paul <lyude@xxxxxxxxxx> >> > > > Signed-off-by: Lee Shawn C <shawn.c.lee@xxxxxxxxx> >> > > > --- >> > > > drivers/gpu/drm/i915/display/intel_dp_mst.c | 24 >> > > > ++++++++++++++++++++- >> > > > 1 file changed, 23 insertions(+), 1 deletion(-) >> > > > >> > > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c >> > > > b/drivers/gpu/drm/i915/display/intel_dp_mst.c >> > > > index 61605eb8c2af..68697f463dab 100644 >> > > > --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c >> > > > +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c >> > > > @@ -609,6 +609,26 @@ static int intel_dp_mst_get_modes(struct >> > > > drm_connector >> > > > *connector) >> > > > return intel_dp_mst_get_ddc_modes(connector); >> > > > } >> > > > >> > > > +static bool >> > > > +intel_dp_mst_mode_clock_exceed_pbn_bandwidth(struct drm_connector >> > > > *connector, int clock, int bpp) >> > > > +{ >> > > > + struct intel_connector *intel_connector = >> > > > to_intel_connector(connector); >> > > > + struct intel_dp *intel_dp = intel_connector->mst_port; >> > > > + struct drm_dp_mst_topology_mgr *mgr = &intel_dp->mst_mgr; >> > > > + struct drm_dp_mst_port *port = (to_intel_connector(connector))->port; >> > > > + bool ret = false; >> > > > + >> > > > + if (!mgr) >> > > > + return ret; >> > > > + >> > > > + mutex_lock(&mgr->lock); >> > > >> > > This isn't the right lock for this - mgr->lock protects the topology >> > > layout (e.g. drm_dp_mst_port.mstb, drm_dp_mst_port.next, and >> > > drm_dp_mst_branch.ports). port->full_pbn is protected under >> > > &drm_dp_mst_topology_mgr.base.lock (not drm_dp_mst_topology_mgr.lock), so >> > > you need to first add a version of .mode_valid() to struct >> > > drm_connector_helper_funcs that accepts a drm_modeset_acquire_ctx so you >> > > can use that to safely grab &drm_dp_mst_topology_mgr.base.lock. >> > > >> > >> > Thanks for comments! I will correct the lock to protect port->full_pbn. >> > >> > > > + if (port->full_pbn) >> > > >> > > Also - there's no reason to check if (port->full_pbn) here, so long as >> > > you're holding the right locks this should always be populated by the time >> > > we create the drm_connector for the MST port (if it's not, that's a bug >> > > that needs to be fixed). >> > > >> > >> > Just want to make sure full_pbn value is greater than zero. As you mention >> > in another patch, it's hard to predict sink report full or available PBN >> > properly. >> >> Sorry this took me a little while to respond to, crunch time came up at work. >> Anyway-have you seen issues with full_pbn reporting on hubs? I've seen plenty >> of problems with available_pbn reporting, but the reason we switched over to >> full_pbn in the first place is because that seemed to be the one hubs reported >> reliably. We actually make the assumption full_pbn is always > 0 if >> something's connected in some places in the MST helpers, so if we've got cases >> of full_pbn lying as well on some hubs we might want to fix that. > >We have at least one full_pbn==0 issue in ci: ><4>[ 5.061345] WARNING: CPU: 0 PID: 376 at drivers/gpu/drm/drm_dp_mst_topology.c:4889 drm_dp_mst_atomic_check_mstb_bw_limit+0x193/0x1c0 > >https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_8460/fi-kbl-7560u/boot0.txt > >Dunno if that's the MST device reporting zero or due to some other >bug, but at least CI is currently borked on that machine. Thanks for sharing! It will be good to keep checking full_pbn to avoid unexpected issue. BTW, I just upload patch v2. Could you please share your comments about that? Best regards, Shawn _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx