linux-kernel - Re: [PATCH] pinctrl: meson: define the pull up/down resistor value as 60 kOhm

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Message-ID: <769e7524-c1fc-4364-a6e8-e0d0315f9514@linaro.org>
Date: Mon, 31 Mar 2025 08:41:00 +0200
From: neil.armstrong@...aro.org
To: Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
 linux-amlogic@...ts.infradead.org, linux-gpio@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linus.walleij@...aro.org
Subject: Re: [PATCH] pinctrl: meson: define the pull up/down resistor value as
 60 kOhm

On 29/03/2025 20:01, Martin Blumenstingl wrote:
> The public datasheets of the following Amlogic SoCs describe a typical
> resistor value for the built-in pull up/down resistor:
> - Meson8/8b/8m2: not documented
> - GXBB (S905): 60 kOhm
> - GXL (S905X): 60 kOhm
> - GXM (S912): 60 kOhm
> - G12B (S922X): 60 kOhm
> - SM1 (S905D3): 60 kOhm
> 
> The public G12B and SM1 datasheets additionally state min and max
> values:
> - min value: 50 kOhm for both, pull-up and pull-down
> - max value for the pull-up: 70 kOhm
> - max value for the pull-down: 130 kOhm
> 
> Use 60 kOhm in the pinctrl-meson driver as well so it's shown in the
> debugfs output. It may not be accurate for Meson8/8b/8m2 but in reality
> 60 kOhm is closer to the actual value than 1 Ohm.
> 
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> ---
>   drivers/pinctrl/meson/pinctrl-meson.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pinctrl/meson/pinctrl-meson.c b/drivers/pinctrl/meson/pinctrl-meson.c
> index 253a0cc57e39..e5a32a0532ee 100644
> --- a/drivers/pinctrl/meson/pinctrl-meson.c
> +++ b/drivers/pinctrl/meson/pinctrl-meson.c
> @@ -487,7 +487,7 @@ static int meson_pinconf_get(struct pinctrl_dev *pcdev, unsigned int pin,
>   	case PIN_CONFIG_BIAS_PULL_DOWN:
>   	case PIN_CONFIG_BIAS_PULL_UP:
>   		if (meson_pinconf_get_pull(pc, pin) == param)
> -			arg = 1;
> +			arg = 60000;
>   		else
>   			return -EINVAL;
>   		break;

Nice finding !

Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>