2022-09-22 13:07:11

by Philippe Schenker

Subject: [PATCH 4/4] drm/bridge: lt8912b: clarify lvds output status

From: Francesco Dolcini <[email protected]>

Add comments on the lt8912_write_lvds_config() config to document the
current settings and to make it clear that this is a hardcoded
configuration not relevant for the HDMI output (could be removed without
affecting the HDMI port).

No changes on the actual register writes.

Signed-off-by: Francesco Dolcini <[email protected]>
Signed-off-by: Philippe Schenker <[email protected]>
---

drivers/gpu/drm/bridge/lontium-lt8912b.c | 26 ++++++++++++++++--------
1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/bridge/lontium-lt8912b.c b/drivers/gpu/drm/bridge/lontium-lt8912b.c
index 5968f4af190b..3e870d45f881 100644
--- a/drivers/gpu/drm/bridge/lontium-lt8912b.c
+++ b/drivers/gpu/drm/bridge/lontium-lt8912b.c
@@ -165,24 +165,32 @@ static int lt8912_write_rxlogicres_config(struct lt8912 *lt)
return ret;
};

+/* enable LVDS output with some hardcoded configuration, not required for the HDMI output */
static int lt8912_write_lvds_config(struct lt8912 *lt)
{
const struct reg_sequence seq[] = {
+ // lvds power up
{0x44, 0x30},
{0x51, 0x05},
- {0x50, 0x24},
- {0x51, 0x2d},
- {0x52, 0x04},
- {0x69, 0x0e},
+
+ // core pll bypass
+ {0x50, 0x24}, // cp=50uA
+ {0x51, 0x2d}, // Pix_clk as reference, second order passive LPF PLL
+ {0x52, 0x04}, // loopdiv=0, use second-order PLL
+ {0x69, 0x0e}, // CP_PRESET_DIV_RATIO
{0x69, 0x8e},
{0x6a, 0x00},
- {0x6c, 0xb8},
+ {0x6c, 0xb8}, // RGD_CP_SOFT_K_EN,RGD_CP_SOFT_K[13:8]
{0x6b, 0x51},
- {0x04, 0xfb},
+
+ {0x04, 0xfb}, // core pll reset
{0x04, 0xff},
- {0x7f, 0x00},
- {0xa8, 0x13},
- {0x02, 0xf7},
+
+ // scaler bypass
+ {0x7f, 0x00}, // disable scaler
+ {0xa8, 0x13}, // 0x13: JEIDA, 0x33: VESA
+
+ {0x02, 0xf7}, // lvds pll reset
{0x02, 0xff},
{0x03, 0xcf},
{0x03, 0xff},
--
2.37.3

2022-09-22 19:27:36

by Adrien Grassein

Subject: Re: [PATCH 4/4] drm/bridge: lt8912b: clarify lvds output status

Le jeu. 22 sept. 2022 à 14:43, Philippe Schenker <[email protected]> a écrit :
>
> From: Francesco Dolcini <[email protected]>
>
> Add comments on the lt8912_write_lvds_config() config to document the
> current settings and to make it clear that this is a hardcoded
> configuration not relevant for the HDMI output (could be removed without
> affecting the HDMI port).
>
> No changes on the actual register writes.
>
> Signed-off-by: Francesco Dolcini <[email protected]>
> Signed-off-by: Philippe Schenker <[email protected]>
Acked-by: Adrien Grassein <[email protected]>
> ---
>
> drivers/gpu/drm/bridge/lontium-lt8912b.c | 26 ++++++++++++++++--------
> 1 file changed, 17 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/lontium-lt8912b.c b/drivers/gpu/drm/bridge/lontium-lt8912b.c
> index 5968f4af190b..3e870d45f881 100644
> --- a/drivers/gpu/drm/bridge/lontium-lt8912b.c
> +++ b/drivers/gpu/drm/bridge/lontium-lt8912b.c
> @@ -165,24 +165,32 @@ static int lt8912_write_rxlogicres_config(struct lt8912 *lt)
> return ret;
> };
>
> +/* enable LVDS output with some hardcoded configuration, not required for the HDMI output */
> static int lt8912_write_lvds_config(struct lt8912 *lt)
> {
> const struct reg_sequence seq[] = {
> + // lvds power up
> {0x44, 0x30},
> {0x51, 0x05},
> - {0x50, 0x24},
> - {0x51, 0x2d},
> - {0x52, 0x04},
> - {0x69, 0x0e},
> +
> + // core pll bypass
> + {0x50, 0x24}, // cp=50uA
> + {0x51, 0x2d}, // Pix_clk as reference, second order passive LPF PLL
> + {0x52, 0x04}, // loopdiv=0, use second-order PLL
> + {0x69, 0x0e}, // CP_PRESET_DIV_RATIO
> {0x69, 0x8e},
> {0x6a, 0x00},
> - {0x6c, 0xb8},
> + {0x6c, 0xb8}, // RGD_CP_SOFT_K_EN,RGD_CP_SOFT_K[13:8]
> {0x6b, 0x51},
> - {0x04, 0xfb},
> +
> + {0x04, 0xfb}, // core pll reset
> {0x04, 0xff},
> - {0x7f, 0x00},
> - {0xa8, 0x13},
> - {0x02, 0xf7},
> +
> + // scaler bypass
> + {0x7f, 0x00}, // disable scaler
> + {0xa8, 0x13}, // 0x13: JEIDA, 0x33: VESA
> +
> + {0x02, 0xf7}, // lvds pll reset
> {0x02, 0xff},
> {0x03, 0xcf},
> {0x03, 0xff},
> --
> 2.37.3
>