[PATCH v12 6/8] drm/mediatek: enable dither function

[Yongqiang Niu]

On Fri, 2021-01-29 at 14:24 +0800, Hsin-Yi Wang wrote:
> On Fri, Jan 29, 2021 at 9:33 AM CK Hu <ck.hu at mediatek.com> wrote:
> >
> > Hi, Hsin-Yi:
> >
> > On Thu, 2021-01-28 at 19:23 +0800, Hsin-Yi Wang wrote:
> > > From: Yongqiang Niu <yongqiang.niu at mediatek.com>
> > >
> > > for 5 or 6 bpc panel, we need enable dither function
> > > to improve the display quality
> > >
> > > Signed-off-by: Yongqiang Niu <yongqiang.niu at mediatek.com>
> > > Signed-off-by: Hsin-Yi Wang <hsinyi at chromium.org>
> > > ---
> > >  drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c | 15 +++++++++++++--
> > >  1 file changed, 13 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> > > index ac2cb25620357..6c8f246380a74 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> > > +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> > > @@ -53,6 +53,7 @@
> > >  #define DITHER_EN                            BIT(0)
> > >  #define DISP_DITHER_CFG                              0x0020
> > >  #define DITHER_RELAY_MODE                    BIT(0)
> > > +#define DITHER_ENGINE_EN                     BIT(1)
> > >  #define DISP_DITHER_SIZE                     0x0030
> > >
> > >  #define LUT_10BIT_MASK                               0x03ff
> > > @@ -314,9 +315,19 @@ static void mtk_dither_config(struct device *dev, unsigned int w,
> > >                             unsigned int bpc, struct cmdq_pkt *cmdq_pkt)
> > >  {
> > >       struct mtk_ddp_comp_dev *priv = dev_get_drvdata(dev);
> > > +     bool enable = (bpc == 5 || bpc == 6);
> >
> > I strongly believe that dither function in dither is identical to the
> > one in gamma and od, and in mtk_dither_set_common(), 'bpc >=
> > MTK_MIN_BPC' is valid, so I believe we need not to limit bpc to 5 or 6.
> > But we should consider the case that bpc is invalid in
> > mtk_dither_set_common(). Invalid case in gamma and od use different way
> > to process. For gamma, dither is default relay mode, so invalid bpc
> > would do nothing in mtk_dither_set_common() and result in relay mode.
> > For od, it set to relay mode first, them invalid bpc would do nothing in
> > mtk_dither_set_common() and result in relay mode. I would like dither,
> > gamma and od to process invalid bpc in the same way. One solution is to
> > set relay mode in mtk_dither_set_common() for invalid bpc.
> >
> > Regards,
> > CK
> >
> 
> I modify the mtk_dither_config() to follow:
> 
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> index ac2cb25620357..5b7fcedb9f9a8 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> @@ -53,6 +53,7 @@
>  #define DITHER_EN                              BIT(0)
>  #define DISP_DITHER_CFG                                0x0020
>  #define DITHER_RELAY_MODE                      BIT(0)
> +#define DITHER_ENGINE_EN                       BIT(1)
>  #define DISP_DITHER_SIZE                       0x0030
> 
>  #define LUT_10BIT_MASK                         0x03ff
> @@ -166,6 +167,8 @@ void mtk_dither_set_common(void __iomem *regs,
> struct cmdq_client_reg *cmdq_reg,
>                               DITHER_ADD_LSHIFT_G(MTK_MAX_BPC - bpc),
>                               cmdq_reg, regs, DISP_DITHER_16);
>                 mtk_ddp_write(cmdq_pkt, dither_en, cmdq_reg, regs, cfg);
> +       } else {
> +               mtk_ddp_write(cmdq_pkt, DITHER_RELAY_MODE, cmdq_reg, regs, cfg);
>         }
>  }
> 
> @@ -315,8 +318,12 @@ static void mtk_dither_config(struct device *dev,
> unsigned int w,
>  {
>         struct mtk_ddp_comp_dev *priv = dev_get_drvdata(dev);
> 
> -       mtk_ddp_write(cmdq_pkt, h << 16 | w, &priv->cmdq_reg,
> priv->regs, DISP_DITHER_SIZE);
> -       mtk_ddp_write(cmdq_pkt, DITHER_RELAY_MODE, &priv->cmdq_reg,
> priv->regs, DISP_DITHER_CFG);
> +       mtk_ddp_write(cmdq_pkt, h << 16 | w, &priv->cmdq_reg, priv->regs,
> +                     DISP_DITHER_SIZE);
> +       mtk_ddp_write(cmdq_pkt, DITHER_RELAY_MODE, &priv->cmdq_reg, priv->regs,
> +                     DISP_DITHER_CFG);
> +       mtk_dither_set_common(priv->regs, &priv->cmdq_reg, bpc, DISP_DITHER_CFG,
> +                              DITHER_ENGINE_EN, cmdq_pkt);
>  }
> 
> So now, not only bpc==5 or 6, but all valid bpc, dither config will
> call mtk_dither_set_common() with the flag DITHER_ENGINE_EN(BIT(1)).
> od config will call mtk_dither_set_common() with the flag
> DISP_DITHERING(BIT(2)).
> Additionally for 8173, gamma config will call mtk_dither_set_common()
> with the flag DISP_DITHERING (BIT(2))
> 
> For invalid mode all of them will be DITHER_RELAY_MODE.
> 
> Just to make sure that this follows the spec? thanks
> 

for mt8173 gamma, there is no relay mode, only dither enable or not(bit
2).
for mt8183 dither, there is dither enable bit 1, and relay mode bit 0


> > >
> > > -     mtk_ddp_write(cmdq_pkt, h << 16 | w, &priv->cmdq_reg, priv->regs, DISP_DITHER_SIZE);
> > > -     mtk_ddp_write(cmdq_pkt, DITHER_RELAY_MODE, &priv->cmdq_reg, priv->regs, DISP_DITHER_CFG);
> > > +     if (enable) {
> > > +             mtk_dither_set_common(priv->regs, &priv->cmdq_reg, bpc,
> > > +                                   DISP_DITHER_CFG, DITHER_ENGINE_EN,
> > > +                                   cmdq_pkt);
> > > +     } else {
> > > +             mtk_ddp_write(cmdq_pkt, DITHER_RELAY_MODE, &priv->cmdq_reg,
> > > +                           priv->regs, DISP_DITHER_CFG);
> > > +     }
> > > +
> > > +     mtk_ddp_write(cmdq_pkt, h << 16 | w, &priv->cmdq_reg, priv->regs,
> > > +                   DISP_DITHER_SIZE);
> > >  }
> > >
> > >  static void mtk_dither_start(struct device *dev)
> >