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

[Dmitry Baryshkov]

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?

> > > +}
> > > +
> > > +static void msm_dp_ctrl_config_ctrl_link(struct msm_dp_ctrl_private *ctrl)
> > > +{
> > > +	u32 config = 0;
> > >   	const u8 *dpcd = ctrl->panel->dpcd;
> > >   	/* Default-> LSCLK DIV: 1/4 LCLK  */
> > >   	config |= (2 << DP_CONFIGURATION_CTRL_LSCLK_DIV_SHIFT);
> > > -	if (ctrl->panel->msm_dp_mode.out_fmt_is_yuv_420)
> > > -		config |= DP_CONFIGURATION_CTRL_RGB_YUV; /* YUV420 */
> > > -
> > >   	/* Scrambler reset enable */
> > >   	if (drm_dp_alternate_scrambler_reset_cap(dpcd))
> > >   		config |= DP_CONFIGURATION_CTRL_ASSR;
> > > -	tbd = msm_dp_link_get_test_bits_depth(ctrl->link,
> > > -			ctrl->panel->msm_dp_mode.bpp);
> > > -
> > > -	config |= tbd << DP_CONFIGURATION_CTRL_BPC_SHIFT;
> > > -
> > >   	/* Num of Lanes */
> > >   	config |= ((ctrl->link->link_params.num_lanes - 1)
> > >   			<< DP_CONFIGURATION_CTRL_NUM_OF_LANES_SHIFT);
> > > @@ -421,10 +436,7 @@ static void msm_dp_ctrl_config_ctrl(struct msm_dp_ctrl_private *ctrl)
> > >   	config |= DP_CONFIGURATION_CTRL_STATIC_DYNAMIC_CN;
> > >   	config |= DP_CONFIGURATION_CTRL_SYNC_ASYNC_CLK;
> > > -	if (ctrl->panel->psr_cap.version)
> > > -		config |= DP_CONFIGURATION_CTRL_SEND_VSC;
> > > -
> > > -	drm_dbg_dp(ctrl->drm_dev, "DP_CONFIGURATION_CTRL=0x%x\n", config);
> > > +	drm_dbg_dp(ctrl->drm_dev, "link DP_CONFIGURATION_CTRL=0x%x\n", config);
> > >   	msm_dp_write_link(ctrl, REG_DP_CONFIGURATION_CTRL, config);
> > >   }
> > > @@ -450,7 +462,8 @@ static void msm_dp_ctrl_configure_source_params(struct msm_dp_ctrl_private *ctrl
> > >   	msm_dp_ctrl_lane_mapping(ctrl);
> > >   	msm_dp_setup_peripheral_flush(ctrl);
> > > -	msm_dp_ctrl_config_ctrl(ctrl);
> > > +	msm_dp_ctrl_config_ctrl_link(ctrl);
> > > +	msm_dp_ctrl_config_ctrl_streams(ctrl, ctrl->panel);
> > >   	test_bits_depth = msm_dp_link_get_test_bits_depth(ctrl->link, ctrl->panel->msm_dp_mode.bpp);
> > >   	colorimetry_cfg = msm_dp_link_get_colorimetry_config(ctrl->link);
> > > @@ -1628,7 +1641,7 @@ static int msm_dp_ctrl_link_train(struct msm_dp_ctrl_private *ctrl,
> > >   	u8 assr;
> > >   	struct msm_dp_link_info link_info = {0};
> > > -	msm_dp_ctrl_config_ctrl(ctrl);
> > > +	msm_dp_ctrl_config_ctrl_link(ctrl);
> > >   	link_info.num_lanes = ctrl->link->link_params.num_lanes;
> > >   	link_info.rate = ctrl->link->link_params.rate;
> > > 
> > > -- 
> > > 2.43.0
> > > 
> > 
> 

-- 
With best wishes
Dmitry