Re: [PATCH v3] drm/dp_mst: Fix return code on sideband message failure

[khsieh]

On 2021-07-07 01:37, Jani Nikula wrote:
> On Tue, 06 Jul 2021, Kuogee Hsieh <khsieh@xxxxxxxxxxxxxx> wrote:
> > From: Rajkumar Subbiah <rsubbia@xxxxxxxxxxxxxx>
> >
> > Commit 2f015ec6eab6 ("drm/dp_mst: Add sideband down request tracing +
> > selftests") added some debug code for sideband message tracing. But
> > it seems to have unintentionally changed the behavior on sideband 
> > message
> > failure. It catches and returns failure only if DRM_UT_DP is enabled.
> > Otherwise it ignores the error code and returns success. So on an MST
> > unplug, the caller is unaware that the clear payload message failed 
> > and
> > ends up waiting for 4 seconds for the response. Fixes the issue by
> > returning the proper error code.
> >
> > Changes in V2:
> > -- Revise commit text as review comment
> > -- add Fixes text
> >
> > Changes in V3:
> > -- remove "unlikely" optimization
> >
> > Fixes: 2f015ec6eab6 ("drm/dp_mst: Add sideband down request tracing + 
> > selftests")
> >
> > Signed-off-by: Rajkumar Subbiah <rsubbia@xxxxxxxxxxxxxx>
> > Signed-off-by: Kuogee Hsieh <khsieh@xxxxxxxxxxxxxx>
> >
> > Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
>
> Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx>
>
>
> > ---
Lyude,
Any comments from you?
Thanks,

> >  drivers/gpu/drm/drm_dp_mst_topology.c | 10 ++++++----
> >  1 file changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c 
> > b/drivers/gpu/drm/drm_dp_mst_topology.c
> > index 1590144..df91110 100644
> > --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> > @@ -2887,11 +2887,13 @@ static int process_single_tx_qlock(struct 
> > drm_dp_mst_topology_mgr *mgr,
> >  	idx += tosend + 1;
> >
> >  	ret = drm_dp_send_sideband_msg(mgr, up, chunk, idx);
> > -	if (unlikely(ret) && drm_debug_enabled(DRM_UT_DP)) {
> > -		struct drm_printer p = drm_debug_printer(DBG_PREFIX);
> > +	if (ret) {
> > +		if (drm_debug_enabled(DRM_UT_DP)) {
> > +			struct drm_printer p = drm_debug_printer(DBG_PREFIX);
> >
> > -		drm_printf(&p, "sideband msg failed to send\n");
> > -		drm_dp_mst_dump_sideband_msg_tx(&p, txmsg);
> > +			drm_printf(&p, "sideband msg failed to send\n");
> > +			drm_dp_mst_dump_sideband_msg_tx(&p, txmsg);
> > +		}
> >  		return ret;
> >  	}