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

On Fri, Jan 29, 2021 at 9:33 AM CK Hu [off-list ref] wrote:

Hi, Hsin-Yi:

On Thu, 2021-01-28 at 19:23 +0800, Hsin-Yi Wang wrote:

quoted

From: Yongqiang Niu <redacted>

for 5 or 6 bpc panel, we need enable dither function
to improve the display quality

Signed-off-by: Yongqiang Niu <redacted>
Signed-off-by: Hsin-Yi Wang <redacted>
---
 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

quoted

-     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)

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