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

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Date:   Thu, 28 Jan 2021 15:59:30 +0800
From:   Yongqiang Niu <yongqiang.niu@...iatek.com>
To:     CK Hu <ck.hu@...iatek.com>
CC:     Hsin-Yi Wang <hsinyi@...omium.org>,
        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@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v11 7/9] drm/mediatek: enable dither function

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


> 
> 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)
> 
>