Re: [Intel-gfx] [PATCH v3] drm/i915/mst: filter out the display mode exceed sink's capability
On Fri, 2020-05-22, 06:35 p.m, Lyude Paul wrote:
>On Fri, 2020-05-22 at 14:35 -0400, Lyude Paul wrote:
>>
>> On Tue, 2020-05-19 at 11:56 +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 ("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.
>> >
>> > v2: Using mgr->base.lock to protect full_pbn.
>> > v3: Add ctx lock.
>> >
>> > Cc: Manasi Navare
>> > Cc: Jani Nikula
>> > Cc: Ville Syrjala
>> > Cc: Cooper Chiou
>> > Cc: Lyude Paul
>> > Signed-off-by: Lee Shawn C
>> > ---
>> > drivers/gpu/drm/i915/display/intel_dp_mst.c | 30
>> > -
>> > 1 file changed, 29 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 74559379384a..6b6f7eef5b68 100644
>> > --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
>> > +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
>> > @@ -611,6 +611,32 @@ 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 = _dp->mst_mgr;
>> > + struct drm_dp_mst_port *port = (to_intel_connector(connector))->port;
>> > + struct drm_modeset_acquire_ctx ctx;
>> > + bool ret = false;
>> > +
>> > + if (!mgr)
>> > + return ret;
>> > +
>> > + drm_modeset_acquire_init(, 0);
>> > +
>> > + drm_modeset_lock(>base.lock, );
>> > + if (port->full_pbn)
>> > + ret = (drm_dp_calc_pbn_mode(clock, bpp, false) > port-
>> > > full_pbn);
>> > + drm_modeset_unlock(>base.lock);
>> > +
>> > + drm_modeset_drop_locks();
>> > + drm_modeset_acquire_fini();
>> > +
>> > + return ret;
>> > +}
>>
>> Sorry to do this, but this still isn't right :s, and will likely end
>> up deadlocking. I'm going to write up a fixed version of this patch
>> and add you in the Co-developed-by: tag, shouldn't take too long for
>> me to do so I can send it out today
>
>Completely forgot to actually explain what was wrong here - this creates an
>acquisition context that would be separate from the caller's lock acquisition
>context. So, drm_helper_probe_single_connector_modes() would grab
>connection_mutex before calling the hook, and since it's not using an
>acquisition context we could potentially deadlock when locking >base.lock
>if another thread locked >base.lock before connection_mutex. If we add a
>lock acquisition context to drm_helper_probe_single_connector_modes and use
>that to grab >base.lock, the ww-mutex code can detect the deadlock and
>give us a chance to back off and try again.
>
>anyway-i'll send out the new version of the patch asap
>
I already test these 2 patches from
https://patchwork.freedesktop.org/series/77573/.
Here is my test env.
1. DUT with DP 1.2 support max 4k@60fps output.
2. MST hub with HDMI 1.4 support max 4k@30fps output.
3. BenQ monitor support HDMI 2.0 max 4k@60fps input.
WIth these 2 changes, DUT works meet our expection.
The resolution from EDID that over 4K@30fps will not be support.
>> > +
>> > static enum drm_mode_status
>> > intel_dp_mst_mode_valid(struct drm_connector *connector,
>> >struct drm_display_mode *mode)
>> > @@ -633,7 +659,9 @@ intel_dp_mst_mode_valid(struct drm_connector
>> > *connector,
>> >max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
>> >mode_rate = intel_dp_link_required(mode->clock, 18);
>> >
>> > - /* TODO - validate mode against available PBN for link */
>> > + if (intel_dp_mst_mode_clock_exceed_pbn_bandwidth(connector, mode-
>> > >clock,
>> > 24))
>> > + return MODE_CLOCK_HIGH;
>> > +
>> >if (mode->clock < 1)
>> >return MODE_CLOCK_LOW;
>> >
>
Best
Re: [Intel-gfx] [PATCH v3] drm/i915/mst: filter out the display mode exceed sink's capability
On Fri, 2020-05-22 at 14:35 -0400, Lyude Paul wrote:
>
> On Tue, 2020-05-19 at 11:56 +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 ("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.
> >
> > v2: Using mgr->base.lock to protect full_pbn.
> > v3: Add ctx lock.
> >
> > Cc: Manasi Navare
> > Cc: Jani Nikula
> > Cc: Ville Syrjala
> > Cc: Cooper Chiou
> > Cc: Lyude Paul
> > Signed-off-by: Lee Shawn C
> > ---
> > drivers/gpu/drm/i915/display/intel_dp_mst.c | 30 -
> > 1 file changed, 29 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 74559379384a..6b6f7eef5b68 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > @@ -611,6 +611,32 @@ 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 = _dp->mst_mgr;
> > + struct drm_dp_mst_port *port = (to_intel_connector(connector))->port;
> > + struct drm_modeset_acquire_ctx ctx;
> > + bool ret = false;
> > +
> > + if (!mgr)
> > + return ret;
> > +
> > + drm_modeset_acquire_init(, 0);
> > +
> > + drm_modeset_lock(>base.lock, );
> > + if (port->full_pbn)
> > + ret = (drm_dp_calc_pbn_mode(clock, bpp, false) > port-
> > > full_pbn);
> > + drm_modeset_unlock(>base.lock);
> > +
> > + drm_modeset_drop_locks();
> > + drm_modeset_acquire_fini();
> > +
> > + return ret;
> > +}
>
> Sorry to do this, but this still isn't right :s, and will likely end up
> deadlocking. I'm going to write up a fixed version of this patch and add you
> in
> the Co-developed-by: tag, shouldn't take too long for me to do so I can send
> it
> out today
Completely forgot to actually explain what was wrong here - this creates an
acquisition context that would be separate from the caller's lock acquisition
context. So, drm_helper_probe_single_connector_modes() would grab
connection_mutex before calling the hook, and since it's not using an
acquisition context we could potentially deadlock when locking >base.lock
if another thread locked >base.lock before connection_mutex. If we add a
lock acquisition context to drm_helper_probe_single_connector_modes and use that
to grab >base.lock, the ww-mutex code can detect the deadlock and give us a
chance to back off and try again.
anyway-i'll send out the new version of the patch asap
> > +
> > static enum drm_mode_status
> > intel_dp_mst_mode_valid(struct drm_connector *connector,
> > struct drm_display_mode *mode)
> > @@ -633,7 +659,9 @@ intel_dp_mst_mode_valid(struct drm_connector *connector,
> > max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
> > mode_rate = intel_dp_link_required(mode->clock, 18);
> >
> > - /* TODO - validate mode against available PBN for link */
> > + if (intel_dp_mst_mode_clock_exceed_pbn_bandwidth(connector, mode-
> > >clock,
> > 24))
> > + return MODE_CLOCK_HIGH;
> > +
> > if (mode->clock < 1)
> > return MODE_CLOCK_LOW;
> >
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Re: [Intel-gfx] [PATCH v3] drm/i915/mst: filter out the display mode exceed sink's capability
On Tue, 2020-05-19 at 11:56 +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 ("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.
>
> v2: Using mgr->base.lock to protect full_pbn.
> v3: Add ctx lock.
>
> Cc: Manasi Navare
> Cc: Jani Nikula
> Cc: Ville Syrjala
> Cc: Cooper Chiou
> Cc: Lyude Paul
> Signed-off-by: Lee Shawn C
> ---
> drivers/gpu/drm/i915/display/intel_dp_mst.c | 30 -
> 1 file changed, 29 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 74559379384a..6b6f7eef5b68 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -611,6 +611,32 @@ 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 = _dp->mst_mgr;
> + struct drm_dp_mst_port *port = (to_intel_connector(connector))->port;
> + struct drm_modeset_acquire_ctx ctx;
> + bool ret = false;
> +
> + if (!mgr)
> + return ret;
> +
> + drm_modeset_acquire_init(, 0);
> +
> + drm_modeset_lock(>base.lock, );
> + if (port->full_pbn)
> + ret = (drm_dp_calc_pbn_mode(clock, bpp, false) > port-
> >full_pbn);
> + drm_modeset_unlock(>base.lock);
> +
> + drm_modeset_drop_locks();
> + drm_modeset_acquire_fini();
> +
> + return ret;
> +}
Sorry to do this, but this still isn't right :s, and will likely end up
deadlocking. I'm going to write up a fixed version of this patch and add you in
the Co-developed-by: tag, shouldn't take too long for me to do so I can send it
out today
> +
> static enum drm_mode_status
> intel_dp_mst_mode_valid(struct drm_connector *connector,
> struct drm_display_mode *mode)
> @@ -633,7 +659,9 @@ intel_dp_mst_mode_valid(struct drm_connector *connector,
> max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
> mode_rate = intel_dp_link_required(mode->clock, 18);
>
> - /* TODO - validate mode against available PBN for link */
> + if (intel_dp_mst_mode_clock_exceed_pbn_bandwidth(connector,
> mode->clock,
> 24))
> + return MODE_CLOCK_HIGH;
> +
> if (mode->clock < 1)
> return MODE_CLOCK_LOW;
>
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