Re: Re: [PATCH v3] i2c: ocores: use devm_ managed clks

[张网]

Hi  Christophe,

Thanks for your suggestions. However, both clk_get_rate and clk_prepare_enable 
will return 0 if i2c->clk is NULL, so I think we may not need to take this issue 
into account.

Regards,
Wang Zhang

"Christophe JAILLET" <christophe.jaillet@xxxxxxxxxx>写道：
> Le 24/05/2023 à 17:43, Wang Zhang a écrit :
> > While it is not entirely clear why the original author implemented this
> > behavior, there may have been certain circumstances or issues that were not
> > apparent to us. It's possible that they were trying to work around a bug by
> > employing an unconventional solution.Using `devm_clk_get_enabled()` rather
> > than devm_clk_get() can automatically track the usage of clocks and free
> > them when they are no longer needed or an error occurs.
> > 
> > fixing it by changing `ocores_i2c_of_probe` to use
> > `devm_clk_get_optional_enabled()` rather than `devm_clk_get()`, changing
> > `goto err_clk' to direct return and removing `err_clk`.
> > 
> > Signed-off-by: Wang Zhang <silver_code@xxxxxxxxxxx>
> > Reviewed-by: Andrew Lunn <andrew@xxxxxxx>
> > ---
> > v2->v3: use `devm_clk_get_optional_enabled()` to manage clks
> > v1->v2: change `ocores_i2c_of_probe` to use `devm_clk_get_enabled()`
> > ---
> >   drivers/i2c/busses/i2c-ocores.c | 57 +++++++++++++--------------------
> >   1 file changed, 22 insertions(+), 35 deletions(-)
> > 
> > diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c
> > index 2e575856c5cd..316d72cde3b9 100644
> > --- a/drivers/i2c/busses/i2c-ocores.c
> > +++ b/drivers/i2c/busses/i2c-ocores.c
> > @@ -552,16 +552,14 @@ static int ocores_i2c_of_probe(struct platform_device *pdev,
> >   							&clock_frequency);
> >   	i2c->bus_clock_khz = 100;
> >   
> > -	i2c->clk = devm_clk_get(&pdev->dev, NULL);
> > +	i2c->clk = devm_clk_get_optional_enabled(&pdev->dev, NULL);
> >   
> > -	if (!IS_ERR(i2c->clk)) {
> > -		int ret = clk_prepare_enable(i2c->clk);
> > -
> > -		if (ret) {
> > -			dev_err(&pdev->dev,
> > -				"clk_prepare_enable failed: %d\n", ret);
> > -			return ret;
> > -		}
> > +	if (IS_ERR(i2c->clk)) {
> > +		dev_err(&pdev->dev,
> > +			"devm_clk_get_optional_enabled failed\n");
> 
> Maybe dev_err_probe() would be nice here. This would log the error code, 
> and filter -EPROBE_DEFER, should it happen.
> 
> > +		return PTR_ERR(i2c->clk);
> > +	}
> > +	if (i2c->clk) {
> >   		i2c->ip_clock_khz = clk_get_rate(i2c->clk) / 1000;
> >   		if (clock_frequency_present)
> >   			i2c->bus_clock_khz = clock_frequency / 1000;
> > @@ -573,7 +571,6 @@ static int ocores_i2c_of_probe(struct platform_device *pdev,
> >   			if (!clock_frequency_present) {
> >   				dev_err(&pdev->dev,
> >   					"Missing required parameter 'opencores,ip-clock-frequency'\n");
> > -				clk_disable_unprepare(i2c->clk);
> >   				return -ENODEV;
> >   			}
> >   			i2c->ip_clock_khz = clock_frequency / 1000;
> > @@ -678,8 +675,7 @@ static int ocores_i2c_probe(struct platform_device *pdev)
> >   		default:
> >   			dev_err(&pdev->dev, "Unsupported I/O width (%d)\n",
> >   				i2c->reg_io_width);
> > -			ret = -EINVAL;
> > -			goto err_clk;
> > +			return -EINVAL;
> >   		}
> >   	}
> >   
> > @@ -710,13 +706,13 @@ static int ocores_i2c_probe(struct platform_device *pdev)
> >   						   pdev->name, i2c);
> >   		if (ret) {
> >   			dev_err(&pdev->dev, "Cannot claim IRQ\n");
> > -			goto err_clk;
> > +			return ret;
> >   		}
> >   	}
> >   
> >   	ret = ocores_init(&pdev->dev, i2c);
> >   	if (ret)
> > -		goto err_clk;
> > +		return ret;
> >   
> >   	/* hook up driver to tree */
> >   	platform_set_drvdata(pdev, i2c);
> > @@ -728,7 +724,7 @@ static int ocores_i2c_probe(struct platform_device *pdev)
> >   	/* add i2c adapter to i2c tree */
> >   	ret = i2c_add_adapter(&i2c->adap);
> >   	if (ret)
> > -		goto err_clk;
> > +		return ret;
> >   
> >   	/* add in known devices to the bus */
> >   	if (pdata) {
> > @@ -737,10 +733,6 @@ static int ocores_i2c_probe(struct platform_device *pdev)
> >   	}
> >   
> >   	return 0;
> > -
> > -err_clk:
> > -	clk_disable_unprepare(i2c->clk);
> > -	return ret;
> >   }
> >   
> >   static int ocores_i2c_remove(struct platform_device *pdev)
> > @@ -755,9 +747,6 @@ static int ocores_i2c_remove(struct platform_device *pdev)
> >   	/* remove adapter & data */
> >   	i2c_del_adapter(&i2c->adap);
> >   
> > -	if (!IS_ERR(i2c->clk))
> > -		clk_disable_unprepare(i2c->clk);
> > -
> >   	return 0;
> >   }
> >   
> > @@ -771,8 +760,7 @@ static int ocores_i2c_suspend(struct device *dev)
> >   	ctrl &= ~(OCI2C_CTRL_EN | OCI2C_CTRL_IEN);
> >   	oc_setreg(i2c, OCI2C_CONTROL, ctrl);
> >   
> > -	if (!IS_ERR(i2c->clk))
> > -		clk_disable_unprepare(i2c->clk);
> > +	clk_disable_unprepare(i2c->clk);
> >   	return 0;
> >   }
> >   
> > @@ -780,19 +768,18 @@ static int ocores_i2c_resume(struct device *dev)
> >   {
> >   	struct ocores_i2c *i2c = dev_get_drvdata(dev);
> >   
> > -	if (!IS_ERR(i2c->clk)) {
> > -		unsigned long rate;
> > -		int ret = clk_prepare_enable(i2c->clk);
> > +	unsigned long rate;
> > +	int ret = clk_prepare_enable(i2c->clk);
> >   
> > -		if (ret) {
> > -			dev_err(dev,
> > -				"clk_prepare_enable failed: %d\n", ret);
> > -			return ret;
> > -		}
> > -		rate = clk_get_rate(i2c->clk) / 1000;
> > -		if (rate)
> > -			i2c->ip_clock_khz = rate;
> > +	if (ret) {
> > +		dev_err(dev,
> > +			"clk_prepare_enable failed: %d\n", ret);
> > +		return ret;
> >   	}
> > +	rate = clk_get_rate(i2c->clk) / 1000;
> 
> Now (because of the devm_clk_get_optional_enabled()), i2c->clk can be 
> NULL, so this would deference a NULL pointer.
> 
> CJ
> 
> 
> > +	if (rate)
> > +		i2c->ip_clock_khz = rate;
> > +
> >   	return ocores_init(dev, i2c);
> >   }
> >