Re: [PATCH RESEND v5 05/25] drm/msm/dp: add support to send ACT packets for MST

[Yongxing Mou]

On 7/12/2026 9:56 PM, Dmitry Baryshkov wrote:
> On Mon, Jun 29, 2026 at 10:14:26PM +0800, Yongxing Mou wrote:
> > From: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> >
> > Whenever virtual channel slot allocation changes, the DP
> > source must send the action control trigger sequence to notify
> > the sink about the same. This would be applicable during the
> > start and stop of the pixel stream. Add the infrastructure
> > to be able to send ACT packets for the DP controller when
> > operating in MST mode.
> >
> > Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> > Signed-off-by: Yongxing Mou <yongxing.mou@xxxxxxxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/msm/dp/dp_ctrl.c    | 44 ++++++++++++++++++++++++++++++++++++-
> >   drivers/gpu/drm/msm/dp/dp_ctrl.h    |  5 ++++-
> >   drivers/gpu/drm/msm/dp/dp_display.c |  3 ++-
> >   drivers/gpu/drm/msm/dp/dp_display.h |  1 +
> >   drivers/gpu/drm/msm/dp/dp_reg.h     |  2 ++
> >   5 files changed, 52 insertions(+), 3 deletions(-)
> >
> > @@ -2623,6 +2656,8 @@ int msm_dp_ctrl_on_stream(struct msm_dp_ctrl *msm_dp_ctrl, struct msm_dp_panel *
> >   
> >   	ctrl = container_of(msm_dp_ctrl, struct msm_dp_ctrl_private, msm_dp_ctrl);
> >   
> > +	ctrl->mst_active = mst_active;
> > +
> >   	pixel_rate_orig = panel->msm_dp_mode.drm_mode.clock;
> >   	pixel_rate = pixel_rate_orig;
> >   
> > @@ -2658,6 +2693,10 @@ int msm_dp_ctrl_on_stream(struct msm_dp_ctrl *msm_dp_ctrl, struct msm_dp_panel *
> >   
> >   	msm_dp_write_link(ctrl, REG_DP_STATE_CTRL, DP_STATE_CTRL_SEND_VIDEO);
> >   
> > +	ret = msm_dp_ctrl_mst_send_act(msm_dp_ctrl, panel);
> > +	if (ret)
> > +		return ret;
>
> Should not we mark mst_active only here?
I'd prefer not to change it here. The flag is needed later in the flow, 
and I'd rather avoid passing it through multiple layers of function 
arguments.. If MST initialization actually fails, I think it's cleaner 
to handle the cleanup through the error path based on the return value.
> > +
> >   	ret = msm_dp_ctrl_wait4video_ready(ctrl);
> >   	if (ret)
> >   		return ret;
> > diff --git a/drivers/gpu/drm/msm/dp/dp_reg.h b/drivers/gpu/drm/msm/dp/dp_reg.h
> > index 310e5a1cc934..6808965878d4 100644
> > --- a/drivers/gpu/drm/msm/dp/dp_reg.h
> > +++ b/drivers/gpu/drm/msm/dp/dp_reg.h
> > @@ -156,6 +156,8 @@
> >   #define DP_CONFIGURATION_CTRL_BPC_SHIFT		(0x08)
> >   #define DP_CONFIGURATION_CTRL_LSCLK_DIV_SHIFT	(0x0D)
> >   
> > +#define REG_DP_MST_ACT				(0x00000500)
>
> It's not that it is a register in its own register space.
Got it. will move this.
> > +
> >   #define REG_DP_SOFTWARE_MVID			(0x00000010)
> >   #define REG_DP_SOFTWARE_NVID			(0x00000018)
> >   #define REG_DP_TOTAL_HOR_VER			(0x0000001C)
> >
> > --
> > 2.43.0