linux-kernel - Re: [PATCH] i2c: hisi: Add support to get clock frequency from clock property

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Message-ID: <739d95c7-28f3-5294-c3db-5acaa7d50823@huawei.com>
Date:   Thu, 22 Sep 2022 19:49:13 +0800
From:   Yicong Yang <yangyicong@...wei.com>
To:     Weilong Chen <chenweilong@...wei.com>, <yangyicong@...ilicon.com>
CC:     <linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i2c: hisi: Add support to get clock frequency from clock
 property

Hi Weilong,

On 2022/9/21 18:15, Weilong Chen wrote:
> Support the driver to obtain clock information by clk_rate or
> clock property. Find clock first, if not, fall back to clk_rate.
> 
> Signed-off-by: Weilong Chen <chenweilong@...wei.com>
> ---
>  drivers/i2c/busses/i2c-hisi.c | 25 ++++++++++++++++++++-----
>  1 file changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-hisi.c b/drivers/i2c/busses/i2c-hisi.c
> index 67031024217c..5e48d4ee0c6d 100644
> --- a/drivers/i2c/busses/i2c-hisi.c
> +++ b/drivers/i2c/busses/i2c-hisi.c
> @@ -8,6 +8,7 @@
>  #include <linux/acpi.h>
>  #include <linux/bits.h>
>  #include <linux/bitfield.h>
> +#include <linux/clk.h>
>  #include <linux/completion.h>
>  #include <linux/i2c.h>
>  #include <linux/interrupt.h>
> @@ -91,6 +92,7 @@ struct hisi_i2c_controller {
>  	void __iomem *iobase;
>  	struct device *dev;
>  	int irq;
> +	struct clk *clk;
>  

Prefer to make this field between @irq and @dev, to make these fields ordered
in an inverted triangle.

>  	/* Intermediates for recording the transfer process */
>  	struct completion *completion;
> @@ -456,10 +458,21 @@ static int hisi_i2c_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> -	ret = device_property_read_u64(dev, "clk_rate", &clk_rate_hz);
> -	if (ret) {
> -		dev_err(dev, "failed to get clock frequency, ret = %d\n", ret);
> -		return ret;
> +	ctlr->clk = devm_clk_get_optional(&pdev->dev, NULL);
> +	if (IS_ERR(ctlr->clk)) {

Use IS_ERR_OR_NULL(), otherwise we cannot get the clock rate.

> +		ret = device_property_read_u64(dev, "clk_rate", &clk_rate_hz);
> +		if (ret) {
> +			dev_err(dev, "failed to get clock frequency, ret = %d\n", ret);
> +			return ret;
> +		}
> +	} else {
> +		ret = clk_prepare_enable(ctlr->clk);

You didn't disable and unprepare the clock on removal.

Use devm_clk_get_optional_enabled() instead then it's managed by devres and the error path
below is unnecessary as well.

BTW, do we really need to prepare and enable the clock? I checked designware-i2c seems it only
gets the clock rate and don't do the prepare and enable operations. I may miss something but
please have a check.

Thanks,
Yicong

> +		if (ret) {
> +			dev_err(dev, "failed to enable clock, ret = %d\n", ret);
> +			return ret;
> +		}
> +
> +		clk_rate_hz = clk_get_rate(ctlr->clk);
>  	}
>  
>  	ctlr->clk_rate_khz = DIV_ROUND_UP_ULL(clk_rate_hz, HZ_PER_KHZ);
> @@ -475,8 +488,10 @@ static int hisi_i2c_probe(struct platform_device *pdev)
>  	i2c_set_adapdata(adapter, ctlr);
>  
>  	ret = devm_i2c_add_adapter(dev, adapter);
> -	if (ret)
> +	if (ret) {
> +		clk_disable_unprepare(ctlr->clk);
>  		return ret;
> +	}
>  
>  	hw_version = readl(ctlr->iobase + HISI_I2C_VERSION);
>  	dev_info(ctlr->dev, "speed mode is %s. hw version 0x%x\n",
>