Re: [PATCH v3 4/7] drm/msm/dpu: add PINGPONG_NONE to disconnect DSC from PINGPONG

[Kuogee Hsieh]

On 5/3/2023 1:03 AM, Marijn Suijten wrote:
> On 2023-05-02 14:02:59, Kuogee Hsieh wrote:
> > During DSC setup, the crossbar mux need to be programmed to engage
> > DSC to specified PINGPONG. Hence during tear down, the crossbar mux
> > need to be reset to disengage DSC from PINGPONG. This patch add
> > PINGPONG_NONE to serve as disable to reset crossbar mux.
> This patch doesn't *just add* PINGPONG_NONE to reset the crossbar; that
> functionality was already available thanks to a `bool enable` function
> parameter.  Instead it should explain why you think PINGPONG_NONE is
> more convenient than passing a bool that warrants this replacement.
> (Hint: I think because you don't have a hw_pp->idx available in the
>   teardown path, and/or its value is not relevant for the disable case
>   anyway.)
>
> In addition I don't see this series use PINGPONG_NONE anywhere yet: will
> that be added in the DSC 1.2 series for DP (to support hotplug)?

PINGPONG_NONE will be used to tear down DSC data path later at DP DSC 
patch series.

Current it is not used because DSI does not do tear down.

> > Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 2 +-
> >   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c  | 7 +++----
> >   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.h  | 1 -
> >   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h | 3 ++-
> >   4 files changed, 6 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > index 1dc5dbe..d9ad334 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > @@ -1839,7 +1839,7 @@ static void dpu_encoder_dsc_pipe_cfg(struct dpu_hw_dsc *hw_dsc,
> >   		hw_pp->ops.setup_dsc(hw_pp);
> >   
> >   	if (hw_dsc->ops.dsc_bind_pingpong_blk)
> > -		hw_dsc->ops.dsc_bind_pingpong_blk(hw_dsc, true, hw_pp->idx);
> > +		hw_dsc->ops.dsc_bind_pingpong_blk(hw_dsc, hw_pp->idx);
> >   
> >   	if (hw_pp->ops.enable_dsc)
> >   		hw_pp->ops.enable_dsc(hw_pp);
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c
> > index 4a6bbcc..3e68d47 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c
> > @@ -157,7 +157,6 @@ static void dpu_hw_dsc_config_thresh(struct dpu_hw_dsc *hw_dsc,
> >   
> >   static void dpu_hw_dsc_bind_pingpong_blk(
> >   		struct dpu_hw_dsc *hw_dsc,
> > -		bool enable,
> >   		const enum dpu_pingpong pp)
> >   {
> >   	struct dpu_hw_blk_reg_map *c = &hw_dsc->hw;
> > @@ -166,13 +165,13 @@ static void dpu_hw_dsc_bind_pingpong_blk(
> >   
> >   	dsc_ctl_offset = DSC_CTL(hw_dsc->idx);
> >   
> > -	if (enable)
> > +	if (pp)
> >   		mux_cfg = (pp - PINGPONG_0) & 0x7;
> >   
> >   	DRM_DEBUG_KMS("%s dsc:%d %s pp:%d\n",
> > -			enable ? "Binding" : "Unbinding",
> > +			pp ? "Binding" : "Unbinding",
> >   			hw_dsc->idx - DSC_0,
> > -			enable ? "to" : "from",
> > +			pp ? "to" : "from",
> >   			pp - PINGPONG_0);
> PINGPONG_NONE - PINGPONG_0 = -1, so this whole debug log likely needs to
> be rewritten for the disable case as we don't know what PINGPONG it is
> being unbound from.  How about:
>
> 	if (pp)
> 		DRM_DEBUG_KMS("Binding dsc:%d to pp:%d\n",
> 				hw_dsc->idx - DSC_0,
> 				pp - PINGPONG_0);
> 	else
> 		DRM_DEBUG_KMS("Unbinding dsc:%d from any pp\n",
> 				hw_dsc->idx - DSC_0);
>
> - Marijn
>
> >   
> >   	DPU_REG_WRITE(c, dsc_ctl_offset, mux_cfg);
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.h
> > index 287ec5f..138080a 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.h
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.h
> > @@ -44,7 +44,6 @@ struct dpu_hw_dsc_ops {
> >   				  struct drm_dsc_config *dsc);
> >   
> >   	void (*dsc_bind_pingpong_blk)(struct dpu_hw_dsc *hw_dsc,
> > -				  bool enable,
> >   				  enum dpu_pingpong pp);
> >   };
> >   
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h
> > index 2d9192a..56826a9 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_mdss.h
> > @@ -191,7 +191,8 @@ enum dpu_dsc {
> >   };
> >   
> >   enum dpu_pingpong {
> > -	PINGPONG_0 = 1,
> > +	PINGPONG_NONE,
> > +	PINGPONG_0,
> >   	PINGPONG_1,
> >   	PINGPONG_2,
> >   	PINGPONG_3,
> > --
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> > a Linux Foundation Collaborative Project