linux-kernel - Re: [PATCH v2 2/3] media: i2c: ov5645: Switch to assigned-clock-rates

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Message-ID: <20200312230051.GA30932@pendragon.ideasonboard.com>
Date:   Fri, 13 Mar 2020 01:00:51 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        NXP Linux Team <linux-imx@....com>,
        Magnus Damm <magnus.damm@...il.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org,
        Fabio Estevam <festevam@...il.com>,
        linux-media@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 2/3] media: i2c: ov5645: Switch to assigned-clock-rates

Hi Prabakhar,

Thank you for the patch.

On Thu, Mar 12, 2020 at 09:12:31PM +0000, Lad Prabhakar wrote:
> This patch switches to assigned-clock-rates for specifying the clock rate.
> The clk-conf.c internally handles setting the clock rate when
> assigned-clock-rates is passed.
> 
> The driver now sets the clock frequency only if the deprecated property
> clock-frequency is defined instead assigned-clock-rates, this is to avoid
> breakage with existing DT binaries.
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> ---
>  drivers/media/i2c/ov5645.c | 24 +++++++++++++++++-------
>  1 file changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/media/i2c/ov5645.c b/drivers/media/i2c/ov5645.c
> index a6c17d1..6cd16c5 100644
> --- a/drivers/media/i2c/ov5645.c
> +++ b/drivers/media/i2c/ov5645.c
> @@ -1055,6 +1055,7 @@ static int ov5645_probe(struct i2c_client *client)
>  	struct device_node *endpoint;
>  	struct ov5645 *ov5645;
>  	u8 chip_id_high, chip_id_low;
> +	bool set_clk = false;
>  	unsigned int i;
>  	u32 xclk_freq;
>  	int ret;
> @@ -1094,10 +1095,17 @@ static int ov5645_probe(struct i2c_client *client)
>  		return PTR_ERR(ov5645->xclk);
>  	}
>  
> -	ret = of_property_read_u32(dev->of_node, "clock-frequency", &xclk_freq);
> +	ret = of_property_read_u32(dev->of_node, "assigned-clock-rates",
> +				   &xclk_freq);

You shouldn't read the assigned-clock-rates property, you should instead
get the rate from the clock with clk_get_rate().

>  	if (ret) {
> -		dev_err(dev, "could not get xclk frequency\n");
> -		return ret;
> +		/* check if deprecated property clock-frequency is defined */
> +		ret = of_property_read_u32(dev->of_node, "clock-frequency",
> +					   &xclk_freq);
> +		if (ret) {
> +			dev_err(dev, "could not get xclk frequency\n");
> +			return ret;
> +		}
> +		set_clk = true;
>  	}
>  
>  	/* external clock must be 24MHz, allow 1% tolerance */
> @@ -1107,10 +1115,12 @@ static int ov5645_probe(struct i2c_client *client)
>  		return -EINVAL;
>  	}
>  
> -	ret = clk_set_rate(ov5645->xclk, xclk_freq);
> -	if (ret) {
> -		dev_err(dev, "could not set xclk frequency\n");
> -		return ret;
> +	if (set_clk) {
> +		ret = clk_set_rate(ov5645->xclk, xclk_freq);
> +		if (ret) {
> +			dev_err(dev, "could not set xclk frequency\n");
> +			return ret;
> +		}
>  	}
>  
>  	for (i = 0; i < OV5645_NUM_SUPPLIES; i++)

-- 
Regards,

Laurent Pinchart