linux-kernel - Re: [PATCH] drm/amdgpu/dm/mst: Fix incorrect usage of drm_dp_add_payload

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Date:   Wed, 05 Oct 2022 14:37:25 -0500
From:   Lyude Paul <lyude@...hat.com>
To:     Rodrigo Siqueira Jordao <Rodrigo.Siqueira@....com>,
        dri-devel@...ts.freedesktop.org, amd-gfx@...ts.freedesktop.org
Cc:     Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Fangzhi Zuo <Jerry.Zuo@....com>, Wayne Lin <Wayne.Lin@....com>,
        Ian Chen <ian.chen@....com>,
        Mikita Lipski <mikita.lipski@....com>,
        Hamza Mahfooz <hamza.mahfooz@....com>,
        Claudio Suarez <cssk@...-c.es>,
        Colin Ian King <colin.i.king@...il.com>,
        Jani Nikula <jani.nikula@...el.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/amdgpu/dm/mst: Fix incorrect usage of
 drm_dp_add_payload_part2()

On Tue, 2022-10-04 at 16:46 -0400, Rodrigo Siqueira Jordao wrote:
> 
> On 2022-10-04 16:24, Lyude Paul wrote:
> > Yikes, it appears somehow I totally made a mistake here. We're currently
> > checking to see if drm_dp_add_payload_part2() returns a non-zero value to
> > indicate success. That's totally wrong though, as this function only
> > returns a zero value on success - not the other way around.
> > 
> > So, fix that.
> > 
> > Signed-off-by: Lyude Paul <lyude@...hat.com>
> > Issue: https://gitlab.freedesktop.org/drm/amd/-/issues/2171
> > Fixes: 4d07b0bc4034 ("drm/display/dp_mst: Move all payload info into the atomic state")
> > ---
> >   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> > index b8077fcd4651..00598def5b39 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> > @@ -297,7 +297,7 @@ bool dm_helpers_dp_mst_send_payload_allocation(
> >   		clr_flag = MST_ALLOCATE_NEW_PAYLOAD;
> >   	}
> >   
> > -	if (enable && drm_dp_add_payload_part2(mst_mgr, mst_state->base.state, payload)) {
> > +	if (enable && drm_dp_add_payload_part2(mst_mgr, mst_state->base.state, payload) == 0) {
> >   		amdgpu_dm_set_mst_status(&aconnector->mst_status,
> >   			set_flag, false);
> >   	} else {
> 
> Hi Lyude,
> 
> Maybe I'm missing something, but I can't find the 
> drm_dp_add_payload_part2() function on amd-staging-drm-next. Which repo 
> are you using?

If it's not on amd-staging-drm-next then it likely hasn't gotten backported to
amd's branch yet and is in drm-misc-next

> 
> Thanks
> Siqueira
> 

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat