Re: [PATCH v4 05/39] drm/msm/dp: splite msm_dp_ctrl_config_ctrl() into link parts and stream parts

[Dmitry Baryshkov]

On Wed, May 20, 2026 at 06:16:05PM +0800, Yongxing Mou wrote:
> 
> 
> On 5/20/2026 5:23 PM, Dmitry Baryshkov wrote:
> > On Tue, May 19, 2026 at 03:46:36PM +0800, Yongxing Mou wrote:
> > > 
> > > 
> > > On 4/12/2026 1:34 AM, Dmitry Baryshkov wrote:
> > > > On Fri, Apr 10, 2026 at 05:33:40PM +0800, Yongxing Mou wrote:
> > > > > The DP_CONFIGURATION_CTRL register contains both link-level and
> > > > > stream-specific fields. Currently, msm_dp_ctrl_config_ctrl() configures
> > > > > all of them together. Separates the configuration into link parts and
> > > > > streams part for support MST.
> > > > > 
> > > > > Signed-off-by: Yongxing Mou <yongxing.mou@xxxxxxxxxxxxxxxx>
> > > > > ---
> > > > >    drivers/gpu/drm/msm/dp/dp_ctrl.c | 43 ++++++++++++++++++++++++++--------------
> > > > >    1 file changed, 28 insertions(+), 15 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> > > > > index 476346e3ac19..85315467b5d0 100644
> > > > > --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> > > > > +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> > > > > @@ -388,26 +388,41 @@ void msm_dp_ctrl_push_idle(struct msm_dp_ctrl *msm_dp_ctrl)
> > > > >    	drm_dbg_dp(ctrl->drm_dev, "mainlink off\n");
> > > > >    }
> > > > > -static void msm_dp_ctrl_config_ctrl(struct msm_dp_ctrl_private *ctrl)
> > > > > +static void msm_dp_ctrl_config_ctrl_streams(struct msm_dp_ctrl_private *ctrl,
> > > > > +					    struct msm_dp_panel *msm_dp_panel)
> > > > >    {
> > > > >    	u32 config = 0, tbd;
> > > > > +
> > > > > +	config = msm_dp_read_link(ctrl, REG_DP_CONFIGURATION_CTRL);
> > > > > +
> > > > > +	if (msm_dp_panel->msm_dp_mode.out_fmt_is_yuv_420)
> > > > > +		config |= DP_CONFIGURATION_CTRL_RGB_YUV; /* YUV420 */
> > > > > +
> > > > > +	tbd = msm_dp_link_get_test_bits_depth(ctrl->link,
> > > > > +					      msm_dp_panel->msm_dp_mode.bpp);
> > > > > +
> > > > > +	config |= tbd << DP_CONFIGURATION_CTRL_BPC_SHIFT;
> > > > > +
> > > > > +	if (msm_dp_panel->psr_cap.version)
> > > > > +		config |= DP_CONFIGURATION_CTRL_SEND_VSC;
> > > > > +
> > > > > +	drm_dbg_dp(ctrl->drm_dev, "stream DP_CONFIGURATION_CTRL=0x%x\n", config);
> > > > > +
> > > > > +	msm_dp_write_link(ctrl, REG_DP_CONFIGURATION_CTRL, config);
> > > > 
> > > > You have an RMW cycle here. Please document what prevents it from racing
> > > > with the concurrent msm_dp_ctrl_config_ctrl_link().
> > > > 
> > > Here protected by mst_lock in MST case. Will add a comment.
> > 
> > And in SST case?
> > 
> Emm, do you think this comments fine?
> 
>   /*
>    * RMW: in SST, config_ctrl_link and config_ctrl_streams are called
>    * sequentially on the same thread. In MST, caller holds mst_lock.
>    */

LGTM

-- 
With best wishes
Dmitry