linux-kernel - Re: [PATCH v11 7/9] drm/mediatek: enable dither function

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Message-ID: <1611822524.23925.4.camel@mtksdaap41>
Date:   Thu, 28 Jan 2021 16:28:44 +0800
From:   CK Hu <ck.hu@...iatek.com>
To:     Hsin-Yi Wang <hsinyi@...omium.org>
CC:     Yongqiang Niu <yongqiang.niu@...iatek.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "David Airlie" <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Devicetree List <devicetree@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v11 7/9] drm/mediatek: enable dither function

On Thu, 2021-01-28 at 16:18 +0800, Hsin-Yi Wang wrote:
> On Thu, Jan 28, 2021 at 4:10 PM Yongqiang Niu
> <yongqiang.niu@...iatek.com> wrote:
> >
> > On Thu, 2021-01-28 at 16:07 +0800, CK Hu wrote:
> > > On Thu, 2021-01-28 at 15:59 +0800, Yongqiang Niu wrote:
> > > > On Thu, 2021-01-28 at 15:42 +0800, CK Hu wrote:
> > > > > Hi, Hsin-Yi:
> > > > >
> > > > > On Thu, 2021-01-28 at 15:28 +0800, Hsin-Yi Wang wrote:
> > > > > > From: Yongqiang Niu <yongqiang.niu@...iatek.com>
> > > > > >
> > > > > > for 5 or 6 bpc panel, we need enable dither function
> > > > > > to improve the display quality
> > > > > >
> > > > > > Signed-off-by: Yongqiang Niu <yongqiang.niu@...iatek.com>
> > > > > > Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> > > > > > ---
> > > > > >  drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c | 44 ++++++++++++++++++++-
> > > > > >  1 file changed, 43 insertions(+), 1 deletion(-)
> > > > > >
> > > > > > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> > > > > > index 8173f709272be..e85625704d611 100644
> > > > > > --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> > > > > > +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> > > > > > @@ -53,7 +53,9 @@
> > > > > >  #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 DITHER_REG(idx)                                (0x100 + (idx) * 4)
> > > > > >
> > > > > >  #define LUT_10BIT_MASK                         0x03ff
> > > > > >
> > > > > > @@ -313,8 +315,48 @@ static void mtk_dither_config(struct device *dev, unsigned int w,
> > > > > >  {
> > > > > >         struct mtk_ddp_comp_dev *priv = dev_get_drvdata(dev);
> > > > > >
> > > > > > +       bool enable = false;
> > > > > > +
> > > > > > +       /* default value for dither reg 5 to 14 */
> > > > > > +       const u32 dither_setting[] = {
> > > > > > +               0x00000000, /* 5 */
> > > > > > +               0x00003002, /* 6 */
> > > > > > +               0x00000000, /* 7 */
> > > > > > +               0x00000000, /* 8 */
> > > > > > +               0x00000000, /* 9 */
> > > > > > +               0x00000000, /* 10 */
> > > > > > +               0x00000000, /* 11 */
> > > > > > +               0x00000011, /* 12 */
> > > > > > +               0x00000000, /* 13 */
> > > > > > +               0x00000000, /* 14 */
> > > > >
> > > > > Could you explain what is this?
> > > >
> > > > this is dither 5 to dither 14 setting
> > > > this will be useless, we just need set dither 5 and dither 7 like
> > > > mtk_ddp_write(cmdq_pkt, 0, comp, DISP_DITHER_5);
> > > > mtk_ddp_write(cmdq_pkt, 0, comp, DISP_DITHER_7);
> > > > other value is same with hardware default value.
> > > >
> > > >
> > > > >
> > > > > > +       };
> > > > > > +
> > > > > > +       if (bpc == 5 || bpc == 6) {
> > > > > > +               enable = true;
> > > > > > +               mtk_ddp_write(cmdq_pkt,
> > > > > > +                             DITHER_LSB_ERR_SHIFT_R(MTK_MAX_BPC - bpc) |
> > > > > > +                             DITHER_ADD_LSHIFT_R(MTK_MAX_BPC - bpc) |
> > > > > > +                             DITHER_NEW_BIT_MODE,
> > > > > > +                             &priv->cmdq_reg, priv->regs, DITHER_REG(15));
> > > > > > +               mtk_ddp_write(cmdq_pkt,
> > > > > > +                             DITHER_LSB_ERR_SHIFT_B(MTK_MAX_BPC - bpc) |
> > > > > > +                             DITHER_ADD_LSHIFT_B(MTK_MAX_BPC - bpc) |
> > > > > > +                             DITHER_LSB_ERR_SHIFT_G(MTK_MAX_BPC - bpc) |
> > > > > > +                             DITHER_ADD_LSHIFT_G(MTK_MAX_BPC - bpc),
> > > > >
> > > > > This result in 0x50505050, but previous version is 0x50504040, so this
> > > > > version is correct and previous version is incorrect?
> > > >
> > > > the new version set r g b 3 channel same, seams more reasonable
> > > >
> > > >
> > >
> > > So all the setting of DISP_DITHER_5, DISP_DITHER_7, DISP_DITHER_15,
> > > DISP_DITHER_16 is identical to mtk_dither_set(), so call
> > > mtk_dither_set() instead of duplication here.
> > >
> >
> > dither enable set in mtk_dither_set is
> > mtk_ddp_write(cmdq_pkt, DISP_DITHERING, comp, CFG);
> >
> > that is different 8183 and mt8192.
> > mt8173 dither enable in gamma is bit2
> > mt8183 and mt8192 dither engine enable is bit 1
> >
> >
> 
> We can still call mtk_dither_set() for bpc is 5 or 6 here, though it
> will be set to bit2,
> but later in mtk_ddp_write(cmdq_pkt, enable ? DITHER_ENGINE_EN :
> DITHER_RELAY_MODE, &priv->cmdq_reg, priv->regs, DISP_DITHER_CFG); it
> will be correct back to bit 1.
> 
> Is this reasonable?

Looks weird. Maybe pass some information into mtk_dither_set() to set
DISP_DITHERING correctly. 

I find one thing need to be fixed. CFG should be lower case.

Regards,
CK

> 
> > > Regards,
> > > CK
> > > > >
> > > > > Regards,
> > > > > CK
> > > > >
> > > > > > +                             &priv->cmdq_reg, priv->regs, DITHER_REG(16));
> > > > > > +       }
> > > > > > +
> > > > > > +
> > > > > > +       if (enable) {
> > > > > > +               u32 idx;
> > > > > > +
> > > > > > +               for (idx = 0; idx < ARRAY_SIZE(dither_setting); idx++)
> > > > > > +                       mtk_ddp_write(cmdq_pkt, dither_setting[idx], &priv->cmdq_reg, priv->regs,
> > > > > > +                                     DITHER_REG(idx + 5));
> > > > > > +       }
> > > > > > +
> > > > > >         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, enable ? DITHER_ENGINE_EN : DITHER_RELAY_MODE, &priv->cmdq_reg, priv->regs, DISP_DITHER_CFG);
> > > > > >  }
> > > > > >
> > > > > >  static void mtk_dither_start(struct device *dev)
> > > > >
> > > > >
> > > >
> > > >
> > >
> > >
> >