Re: [PATCH 1/4] drm/msm/dsi: Adjust pclk rate for compression

[Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>]

On 5/3/2023 1:33 AM, Dmitry Baryshkov wrote:
> On 03/05/2023 04:19, Jessica Zhang wrote:
> > Divide the pclk rate by the compression ratio when DSC is enabled
> >
> > Signed-off-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/msm/dsi/dsi_host.c | 14 ++++++++++----
> >   1 file changed, 10 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c 
> > b/drivers/gpu/drm/msm/dsi/dsi_host.c
> > index 43a5ec33eee8..35c69dbe5f6f 100644
> > --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> > +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> > @@ -561,7 +561,8 @@ void dsi_link_clk_disable_v2(struct msm_dsi_host 
> > *msm_host)
> >       clk_disable_unprepare(msm_host->byte_clk);
> >   }
> > -static unsigned long dsi_get_pclk_rate(const struct drm_display_mode 
> > *mode, bool is_bonded_dsi)
> > +static unsigned long dsi_get_pclk_rate(const struct drm_display_mode 
> > *mode,
> > +        struct drm_dsc_config *dsc, bool is_bonded_dsi)
> >   {
> >       unsigned long pclk_rate;
> > @@ -576,6 +577,11 @@ static unsigned long dsi_get_pclk_rate(const 
> > struct drm_display_mode *mode, bool
> >       if (is_bonded_dsi)
> >           pclk_rate /= 2;
> > +    /* If DSC is enabled, divide pclk by compression ratio */
> > +    if (dsc)
> > +        pclk_rate = DIV_ROUND_UP(pclk_rate,
> > +                dsc->bits_per_component * 3 / msm_dsc_get_bpp_int(dsc));
> > +
>
> Don't we loose precision here?
> Would DIV_ROUND_UP(pclk_rate * bpp, dsc->bpc * 3) be better?

Hi Dmitry,

Acked.

Thanks,

Jessica Zhang

> >       return pclk_rate;
> >   }
> > @@ -585,7 +591,7 @@ unsigned long dsi_byte_clk_get_rate(struct 
> > mipi_dsi_host *host, bool is_bonded_d
> >       struct msm_dsi_host *msm_host = to_msm_dsi_host(host);
> >       u8 lanes = msm_host->lanes;
> >       u32 bpp = dsi_get_bpp(msm_host->format);
> > -    unsigned long pclk_rate = dsi_get_pclk_rate(mode, is_bonded_dsi);
> > +    unsigned long pclk_rate = dsi_get_pclk_rate(mode, msm_host->dsc, 
> > is_bonded_dsi);
> >       u64 pclk_bpp = (u64)pclk_rate * bpp;
> >       if (lanes == 0) {
> > @@ -604,7 +610,7 @@ unsigned long dsi_byte_clk_get_rate(struct 
> > mipi_dsi_host *host, bool is_bonded_d
> >   static void dsi_calc_pclk(struct msm_dsi_host *msm_host, bool 
> > is_bonded_dsi)
> >   {
> > -    msm_host->pixel_clk_rate = dsi_get_pclk_rate(msm_host->mode, 
> > is_bonded_dsi);
> > +    msm_host->pixel_clk_rate = dsi_get_pclk_rate(msm_host->mode, 
> > msm_host->dsc, is_bonded_dsi);
> >       msm_host->byte_clk_rate = dsi_byte_clk_get_rate(&msm_host->base, 
> > is_bonded_dsi,
> >                               msm_host->mode);
> > @@ -634,7 +640,7 @@ int dsi_calc_clk_rate_v2(struct msm_dsi_host 
> > *msm_host, bool is_bonded_dsi)
> >       dsi_calc_pclk(msm_host, is_bonded_dsi);
> > -    pclk_bpp = (u64)dsi_get_pclk_rate(msm_host->mode, is_bonded_dsi) 
> > * bpp;
> > +    pclk_bpp = (u64)dsi_get_pclk_rate(msm_host->mode, msm_host->dsc, 
> > is_bonded_dsi) * bpp;
> >       do_div(pclk_bpp, 8);
> >       msm_host->src_clk_rate = pclk_bpp;
>
> --
> With best wishes
> Dmitry