# \[PATCH\] video: exynos\_dp: increase AUX channel voltage level

- Subsystems: FRAMEBUFFER LAYER, THE REST
- Maintainers: Helge Deller, Linus Torvalds
- List: linux-fbdev
- 2 messages, 2 authors
- Page: https://ratatoskr.run/linux-fbdev/2012/09/13463891/t

## \[PATCH\] video: exynos\_dp: increase AUX channel voltage level

- From: Jingoo Han \<hidden\>
- Date: 2012-09-12 07:52:09 
- Message: https://ratatoskr.run/linux-fbdev/2012/09/13463891.md

```text
The value of AUX channel differential amplitude current is changed
from 8 mA to 16 mA, in order to increase AUX channel voltage level.
In this case, AUX channel voltage level can be changed from 400 mV
to 800 mV, when resistance between AUX TX and RX is 100 ohm.

According to DP spec, although the normative voltage level is 390 mV,
the informative voltage level is 430 mV. So, 800 mV can be helpful
to improve voltage margin of AUX channel.

Signed-off-by: Jingoo Han <redacted>
---
 drivers/video/exynos/exynos_dp_reg.c |    2 +-
 drivers/video/exynos/exynos_dp_reg.h |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/video/exynos/exynos_dp_reg.c b/drivers/video/exynos/exynos_dp_reg.c
index 20e441f..5fd1214 100644
--- a/drivers/video/exynos/exynos_dp_reg.c
+++ b/drivers/video/exynos/exynos_dp_reg.c
@@ -77,7 +77,7 @@ void exynos_dp_init_analog_param(struct exynos_dp_device *dp)
 	writel(reg, dp->reg_base + EXYNOS_DP_ANALOG_CTL_3);
 
 	reg = PD_RING_OSC | AUX_TERMINAL_CTRL_50_OHM |
-		TX_CUR1_2X | TX_CUR_8_MA;
+		TX_CUR1_2X | TX_CUR_16_MA;
 	writel(reg, dp->reg_base + EXYNOS_DP_PLL_FILTER_CTL_1);
 
 	reg = CH3_AMP_400_MV | CH2_AMP_400_MV |
diff --git a/drivers/video/exynos/exynos_dp_reg.h b/drivers/video/exynos/exynos_dp_reg.h
index 125b27c..0e79031 100644
--- a/drivers/video/exynos/exynos_dp_reg.h
+++ b/drivers/video/exynos/exynos_dp_reg.h
@@ -187,7 +187,7 @@
 #define PD_RING_OSC				(0x1 << 6)
 #define AUX_TERMINAL_CTRL_50_OHM		(0x2 << 4)
 #define TX_CUR1_2X				(0x1 << 2)
-#define TX_CUR_8_MA				(0x2 << 0)
+#define TX_CUR_16_MA				(0x3 << 0)
 
 /* EXYNOS_DP_TX_AMP_TUNING_CTL */
 #define CH3_AMP_400_MV				(0x0 << 24)
-- 
1.7.1


```

## Re: \[PATCH\] video: exynos\_dp: increase AUX channel voltage level

- From: Florian Tobias Schandinat \<FlorianSchandinat@gmx.de\>
- Date: 2012-09-23 19:50:01 
- Message: https://ratatoskr.run/linux-fbdev/2012/09/13463892.md

```text
On 09/12/2012 07:52 AM, Jingoo Han wrote:
> The value of AUX channel differential amplitude current is changed
> from 8 mA to 16 mA, in order to increase AUX channel voltage level.
> In this case, AUX channel voltage level can be changed from 400 mV
> to 800 mV, when resistance between AUX TX and RX is 100 ohm.
> 
> According to DP spec, although the normative voltage level is 390 mV,
> the informative voltage level is 430 mV. So, 800 mV can be helpful
> to improve voltage margin of AUX channel.
> 
> Signed-off-by: Jingoo Han <redacted>

Applied. But it might be a good idea to keep the old definition in the
header file for documentation purposes.


Thanks,

Florian Tobias Schandinat

> ---
>  drivers/video/exynos/exynos_dp_reg.c |    2 +-
>  drivers/video/exynos/exynos_dp_reg.h |    2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/video/exynos/exynos_dp_reg.c b/drivers/video/exynos/exynos_dp_reg.c
> index 20e441f..5fd1214 100644
> --- a/drivers/video/exynos/exynos_dp_reg.c
> +++ b/drivers/video/exynos/exynos_dp_reg.c
> @@ -77,7 +77,7 @@ void exynos_dp_init_analog_param(struct exynos_dp_device *dp)
>  	writel(reg, dp->reg_base + EXYNOS_DP_ANALOG_CTL_3);
>  
>  	reg = PD_RING_OSC | AUX_TERMINAL_CTRL_50_OHM |
> -		TX_CUR1_2X | TX_CUR_8_MA;
> +		TX_CUR1_2X | TX_CUR_16_MA;
>  	writel(reg, dp->reg_base + EXYNOS_DP_PLL_FILTER_CTL_1);
>  
>  	reg = CH3_AMP_400_MV | CH2_AMP_400_MV |
> diff --git a/drivers/video/exynos/exynos_dp_reg.h b/drivers/video/exynos/exynos_dp_reg.h
> index 125b27c..0e79031 100644
> --- a/drivers/video/exynos/exynos_dp_reg.h
> +++ b/drivers/video/exynos/exynos_dp_reg.h
> @@ -187,7 +187,7 @@
>  #define PD_RING_OSC				(0x1 << 6)
>  #define AUX_TERMINAL_CTRL_50_OHM		(0x2 << 4)
>  #define TX_CUR1_2X				(0x1 << 2)
> -#define TX_CUR_8_MA				(0x2 << 0)
> +#define TX_CUR_16_MA				(0x3 << 0)
>  
>  /* EXYNOS_DP_TX_AMP_TUNING_CTL */
>  #define CH3_AMP_400_MV				(0x0 << 24)

```