[PATCH] [media] adv7604: Initialize drive strength to default when using DT

[PATCH] [media] adv7604: Initialize drive strength to default when using DT

[Lars-Peter Clausen]

The adv7604 driver platform data contains fields for configuring the drive
strength of the output pins. When probing the driver through DT these
fields are not explicitly initialized, which means they are left at 0. This
is a reserved setting for the drive strength configuration though and can
cause signal integrity issues.

Whether these signal integrity issues are visible depends on the PCB
specifics (e.g. the higher the load capacitance for the output the more
visible the issue). But it has been observed on existing solutions at high
pixel clock rates.

Initialize the drive strength settings to the power-on-reset value of the
device when probing through devicetree to avoid this issue.

Fixes: 0e158be0162b ("adv7604: Add DT support")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
---
 drivers/media/i2c/adv7604.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/media/i2c/adv7604.c b/drivers/media/i2c/adv7604.c
index 5630eb2..a4dc64a 100644
--- a/drivers/media/i2c/adv7604.c
+++ b/drivers/media/i2c/adv7604.c
@@ -3132,6 +3132,9 @@ static int adv76xx_parse_dt(struct adv76xx_state *state)
 	state->pdata.blank_data = 1;
 	state->pdata.op_format_mode_sel = ADV7604_OP_FORMAT_MODE0;
 	state->pdata.bus_order = ADV7604_BUS_ORDER_RGB;
+	state->pdata.dr_str_data = ADV76XX_DR_STR_MEDIUM_HIGH;
+	state->pdata.dr_str_clk = ADV76XX_DR_STR_MEDIUM_HIGH;
+	state->pdata.dr_str_sync = ADV76XX_DR_STR_MEDIUM_HIGH;
 
 	return 0;
 }
-- 
2.1.4

Re: [PATCH] [media] adv7604: Initialize drive strength to default when using DT

[Laurent Pinchart]

Hi Lars,

Thank you for the patch.

On Tuesday 29 Nov 2016 12:23:48 Lars-Peter Clausen wrote:
> The adv7604 driver platform data contains fields for configuring the drive
> strength of the output pins. When probing the driver through DT these
> fields are not explicitly initialized, which means they are left at 0. This
> is a reserved setting for the drive strength configuration though and can
> cause signal integrity issues.
> 
> Whether these signal integrity issues are visible depends on the PCB
> specifics (e.g. the higher the load capacitance for the output the more
> visible the issue). But it has been observed on existing solutions at high
> pixel clock rates.
> 
> Initialize the drive strength settings to the power-on-reset value of the
> device when probing through devicetree to avoid this issue.
> 
> Fixes: 0e158be0162b ("adv7604: Add DT support")
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> ---
>  drivers/media/i2c/adv7604.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/media/i2c/adv7604.c b/drivers/media/i2c/adv7604.c
> index 5630eb2..a4dc64a 100644
> --- a/drivers/media/i2c/adv7604.c
> +++ b/drivers/media/i2c/adv7604.c
> @@ -3132,6 +3132,9 @@ static int adv76xx_parse_dt(struct adv76xx_state
> *state) state->pdata.blank_data = 1;
>  	state->pdata.op_format_mode_sel = ADV7604_OP_FORMAT_MODE0;
>  	state->pdata.bus_order = ADV7604_BUS_ORDER_RGB;
> +	state->pdata.dr_str_data = ADV76XX_DR_STR_MEDIUM_HIGH;
> +	state->pdata.dr_str_clk = ADV76XX_DR_STR_MEDIUM_HIGH;
> +	state->pdata.dr_str_sync = ADV76XX_DR_STR_MEDIUM_HIGH;
> 
>  	return 0;
>  }

-- 
Regards,

Laurent Pinchart

Re: [PATCH] [media] adv7604: Initialize drive strength to default when using DT

[Niklas Söderlund]

Hi Lars,

On 2016-11-29 12:23:48 +0100, Lars-Peter Clausen wrote:
> The adv7604 driver platform data contains fields for configuring the drive
> strength of the output pins. When probing the driver through DT these
> fields are not explicitly initialized, which means they are left at 0. This
> is a reserved setting for the drive strength configuration though and can
> cause signal integrity issues.
> 
> Whether these signal integrity issues are visible depends on the PCB
> specifics (e.g. the higher the load capacitance for the output the more
> visible the issue). But it has been observed on existing solutions at high
> pixel clock rates.
> 
> Initialize the drive strength settings to the power-on-reset value of the
> device when probing through devicetree to avoid this issue.
> 
> Fixes: 0e158be0162b ("adv7604: Add DT support")
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

Tested on Renesas Koelsch board which uses a adv7612 for HDMI input.

Tested-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>

> ---
>  drivers/media/i2c/adv7604.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/media/i2c/adv7604.c b/drivers/media/i2c/adv7604.c
> index 5630eb2..a4dc64a 100644
> --- a/drivers/media/i2c/adv7604.c
> +++ b/drivers/media/i2c/adv7604.c
> @@ -3132,6 +3132,9 @@ static int adv76xx_parse_dt(struct adv76xx_state *state)
>  	state->pdata.blank_data = 1;
>  	state->pdata.op_format_mode_sel = ADV7604_OP_FORMAT_MODE0;
>  	state->pdata.bus_order = ADV7604_BUS_ORDER_RGB;
> +	state->pdata.dr_str_data = ADV76XX_DR_STR_MEDIUM_HIGH;
> +	state->pdata.dr_str_clk = ADV76XX_DR_STR_MEDIUM_HIGH;
> +	state->pdata.dr_str_sync = ADV76XX_DR_STR_MEDIUM_HIGH;
>  
>  	return 0;
>  }
> -- 
> 2.1.4
> 

-- 
Regards,
Niklas Söderlund