linux-kernel - Re: [PATCH v2 1/3] drm/dp_mst: add passthrough_aux to struct drm_dp_mst

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Message-ID: <df2b8017427dc2ebab9bcf70e406d0732ef59299.camel@redhat.com>
Date:   Wed, 10 Aug 2022 17:24:18 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     Hamza Mahfooz <hamza.mahfooz@....com>, linux-kernel@...r.kernel.org
Cc:     Harry Wentland <harry.wentland@....com>,
        Fangzhi Zuo <Jerry.Zuo@....com>, Wayne Lin <Wayne.Lin@....com>,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        hersenxs.wu@....com, Leo Li <sunpeng.li@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Mikita Lipski <mikita.lipski@....com>,
        Claudio Suarez <cssk@...-c.es>,
        Bhawanpreet Lakha <Bhawanpreet.Lakha@....com>,
        Roman Li <Roman.Li@....com>, Ian Chen <ian.chen@....com>,
        Colin Ian King <colin.king@...el.com>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Jani Nikula <jani.nikula@...el.com>,
        Imran Khan <imran.f.khan@...cle.com>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Imre Deak <imre.deak@...el.com>,
        David Zhang <dingchen.zhang@....com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2 1/3] drm/dp_mst: add passthrough_aux to struct
 drm_dp_mst_port

On Wed, 2022-08-10 at 09:23 -0400, Hamza Mahfooz wrote:
> On 2022-08-09 18:01, Lyude Paul wrote:
> > Ah yes of course! Probably should have asked when I gave the r-b :). Also,
> > just so patchwork actually catches it I will say the magic incantation:
> > 
> > Reviewed-by: Lyude Paul <lyude@...hat.com>
> > 
> > Do we want to merge just this patch to drm-misc-next, or do you want to merge
> > the whole series through there? If you'd rather just merge this through amd's
> > branch I'm fine with that as well
> 
> In that case, it is preferable to have all of the patches in this series
> to get merged through amd's branch.\

Sounds totally fine to me! Just make sure to run it by Harry or another amdgpu
maintainer first, and then you should be good to go.

> 
> > 
> > On Tue, 2022-08-09 at 11:15 -0400, Hamza Mahfooz wrote:
> > > Hey Lyude,
> > > 
> > > On 2022-08-05 17:17, Lyude Paul wrote:
> > > > lgtm!
> > > > 
> > > 
> > > Any chance you can apply this to drm-misc-next?
> > > 
> > > > Reviewed-by: Lyude Paul <lyude@...hat.com>
> > > > 
> > > > On Fri, 2022-08-05 at 17:13 -0400, Hamza Mahfooz wrote:
> > > > > Currently, there is no way to identify if DSC pass-through can be
> > > > > enabled and what aux DSC pass-through requests ought to be sent to. So,
> > > > > add a variable to struct drm_dp_mst_port that keeps track of the
> > > > > aforementioned information.
> > > > > 
> > > > > Signed-off-by: Hamza Mahfooz <hamza.mahfooz@....com>
> > > > > ---
> > > > > v2: define DP_DSC_PASSTHROUGH_IS_SUPPORTED
> > > > > ---
> > > > >    drivers/gpu/drm/display/drm_dp_mst_topology.c | 4 +++-
> > > > >    include/drm/display/drm_dp.h                  | 1 +
> > > > >    include/drm/display/drm_dp_mst_helper.h       | 3 +++
> > > > >    3 files changed, 7 insertions(+), 1 deletion(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > > > > index 67b3b9697da7..71915afd9892 100644
> > > > > --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > > > > +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > > > > @@ -5921,8 +5921,10 @@ struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
> > > > >    		/* Enpoint decompression with DP-to-DP peer device */
> > > > >    		if ((endpoint_dsc & DP_DSC_DECOMPRESSION_IS_SUPPORTED) &&
> > > > >    		    (endpoint_fec & DP_FEC_CAPABLE) &&
> > > > > -		    (upstream_dsc & 0x2) /* DSC passthrough */)
> > > > > +		    (upstream_dsc & DP_DSC_PASSTHROUGH_IS_SUPPORTED)) {
> > > > > +			port->passthrough_aux = &immediate_upstream_port->aux;
> > > > >    			return &port->aux;
> > > > > +		}
> > > > >    
> > > > >    		/* Virtual DPCD decompression with DP-to-DP peer device */
> > > > >    		return &immediate_upstream_port->aux;
> > > > > diff --git a/include/drm/display/drm_dp.h b/include/drm/display/drm_dp.h
> > > > > index 9e3aff7e68bb..4d0abe4c7ea9 100644
> > > > > --- a/include/drm/display/drm_dp.h
> > > > > +++ b/include/drm/display/drm_dp.h
> > > > > @@ -239,6 +239,7 @@
> > > > >    
> > > > >    #define DP_DSC_SUPPORT                      0x060   /* DP 1.4 */
> > > > >    # define DP_DSC_DECOMPRESSION_IS_SUPPORTED  (1 << 0)
> > > > > +# define DP_DSC_PASSTHROUGH_IS_SUPPORTED    (1 << 1)
> > > > >    
> > > > >    #define DP_DSC_REV                          0x061
> > > > >    # define DP_DSC_MAJOR_MASK                  (0xf << 0)
> > > > > diff --git a/include/drm/display/drm_dp_mst_helper.h b/include/drm/display/drm_dp_mst_helper.h
> > > > > index 10adec068b7f..4a39c95f8afd 100644
> > > > > --- a/include/drm/display/drm_dp_mst_helper.h
> > > > > +++ b/include/drm/display/drm_dp_mst_helper.h
> > > > > @@ -86,6 +86,8 @@ struct drm_dp_vcpi {
> > > > >     * @next: link to next port on this branch device
> > > > >     * @aux: i2c aux transport to talk to device connected to this port, protected
> > > > >     * by &drm_dp_mst_topology_mgr.base.lock.
> > > > > + * @passthrough_aux: parent aux to which DSC pass-through requests should be
> > > > > + * sent, only set if DSC pass-through is possible.
> > > > >     * @parent: branch device parent of this port
> > > > >     * @vcpi: Virtual Channel Payload info for this port.
> > > > >     * @connector: DRM connector this port is connected to. Protected by
> > > > > @@ -140,6 +142,7 @@ struct drm_dp_mst_port {
> > > > >    	 */
> > > > >    	struct drm_dp_mst_branch *mstb;
> > > > >    	struct drm_dp_aux aux; /* i2c bus for this port? */
> > > > > +	struct drm_dp_aux *passthrough_aux;
> > > > >    	struct drm_dp_mst_branch *parent;
> > > > >    
> > > > >    	struct drm_dp_vcpi vcpi;
> > > > 
> > > 
> > 
> 

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