linux-kernel - Re: [PATCH 07/19] media: i2c: ds90ub953: Speed-up I2C watchdog timer

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Message-ID: <Z4fDfQcnZiHC0Fms@kekkonen.localdomain>
Date: Wed, 15 Jan 2025 14:17:33 +0000
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org, Devarsh Thakkar <devarsht@...com>,
	Jai Luthra <jai.luthra@...asonboard.com>
Subject: Re: [PATCH 07/19] media: i2c: ds90ub953: Speed-up I2C watchdog timer

Moi,

On Fri, Jan 10, 2025 at 11:14:07AM +0200, Tomi Valkeinen wrote:
> From: Jai Luthra <jai.luthra@...asonboard.com>
> 
> On the I2C bus for remote clients (sensors), by default the watchdog
> timer expires in 1s. To allow for a quicker system bring-up time, TI
> recommends to speed it up to 50us [1].
> 
> [1]: Section 7.3.1.1 - https://www.ti.com/lit/gpn/ds90ub953-q1
> 
> Signed-off-by: Jai Luthra <jai.luthra@...asonboard.com>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
> ---
>  drivers/media/i2c/ds90ub953.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/media/i2c/ds90ub953.c b/drivers/media/i2c/ds90ub953.c
> index 99a4852b9381..6c36980e8beb 100644
> --- a/drivers/media/i2c/ds90ub953.c
> +++ b/drivers/media/i2c/ds90ub953.c
> @@ -54,6 +54,10 @@
>  #define UB953_REG_CLKOUT_CTRL0			0x06
>  #define UB953_REG_CLKOUT_CTRL1			0x07
>  
> +#define UB953_REG_I2C_CONTROL2			0x0a
> +#define UB953_REG_I2C_CONTROL2_SDA_OUTPUT_SETUP_SHIFT	4
> +#define UB953_REG_I2C_CONTROL2_BUS_SPEEDUP	BIT(1)
> +
>  #define UB953_REG_SCL_HIGH_TIME			0x0b
>  #define UB953_REG_SCL_LOW_TIME			0x0c
>  
> @@ -1320,6 +1324,13 @@ static int ub953_hw_init(struct ub953_data *priv)
>  	if (ret)
>  		return ret;
>  
> +	v = 0;
> +	v |= 1 << UB953_REG_I2C_CONTROL2_SDA_OUTPUT_SETUP_SHIFT;

BIT()? Or at least 1U <<< ...;.

> +	v |= UB953_REG_I2C_CONTROL2_BUS_SPEEDUP;
> +	ret = ub953_write(priv, UB953_REG_I2C_CONTROL2, v, NULL);

I'd just do this without a temporary variable. If you prefer to keep it, do
assign the first calculated value there first and remove the assignment to
zero.

> +	if (ret)
> +		return ret;

No need for this.

> +
>  	return 0;
>  }
>  
> 

-- 
Terveisin,

Sakari Ailus