linux-kernel - Re: [PATCH] power: reset: at91-reset: free resources on exit path

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Message-ID: <ee7f39b3-8f7a-deb4-b4b2-dfc8e2ba86f9@microchip.com>
Date:   Thu, 1 Apr 2021 14:42:47 +0000
From:   <Claudiu.Beznea@...rochip.com>
To:     <Nicolas.Ferre@...rochip.com>, <sre@...nel.org>,
        <alexandre.belloni@...tlin.com>, <Ludovic.Desroches@...rochip.com>
CC:     <linux-pm@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <lkp@...el.com>,
        <dan.carpenter@...cle.com>
Subject: Re: [PATCH] power: reset: at91-reset: free resources on exit path

On 31.03.2021 11:18, Nicolas Ferre wrote:
> On 09/02/2021 at 12:01, Claudiu Beznea wrote:
>> Free resources on exit path (failure path of probe and remove).
> 
> I'm not sure we can use this driver as a module anyway.
> 
> Otherwise, it looks fine, but isn't it possible to use devm_of_iomap(),
> even in loop, and avoid having to deal with exit path?

For:
reset->rstc_base = of_iomap(pdev->dev.of_node, 0);

it should work.

For the maps in the loop I have to double check. Basically, the struct
resource object to pass to devm_of_iomap() is needed and for this the
pointer to a struct platform_device object corresponding to the node we
look for in the loop is needed. So, I think this cannot be done this way.

> 
>> Reported-by: kernel test robot <lkp@...el.com>
>> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
>> Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
>> ---
>>   drivers/power/reset/at91-reset.c | 25 ++++++++++++++++++++-----
>>   1 file changed, 20 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/power/reset/at91-reset.c
>> b/drivers/power/reset/at91-reset.c
>> index 3ff9d93a5226..2ff7833153b6 100644
>> --- a/drivers/power/reset/at91-reset.c
>> +++ b/drivers/power/reset/at91-reset.c
>> @@ -206,7 +206,8 @@ static int __init at91_reset_probe(struct
>> platform_device *pdev)
>>               if (!reset->ramc_base[idx]) {
>>                   dev_err(&pdev->dev, "Could not map ram controller
>> address\n");
>>                   of_node_put(np);
>> -                return -ENODEV;
>> +                ret = -ENODEV;
>> +                goto unmap;
>>               }
>>               idx++;
>>           }
>> @@ -218,13 +219,15 @@ static int __init at91_reset_probe(struct
>> platform_device *pdev)
>>       reset->args = (u32)match->data;
>>         reset->sclk = devm_clk_get(&pdev->dev, NULL);
>> -    if (IS_ERR(reset->sclk))
>> -        return PTR_ERR(reset->sclk);
>> +    if (IS_ERR(reset->sclk)) {
>> +        ret = PTR_ERR(reset->sclk);
>> +        goto unmap;
>> +    }
>>         ret = clk_prepare_enable(reset->sclk);
>>       if (ret) {
>>           dev_err(&pdev->dev, "Could not enable slow clock\n");
>> -        return ret;
>> +        goto unmap;
>>       }
>>         platform_set_drvdata(pdev, reset);
>> @@ -239,21 +242,33 @@ static int __init at91_reset_probe(struct
>> platform_device *pdev)
>>       ret = register_restart_handler(&reset->nb);
>>       if (ret) {
>>           clk_disable_unprepare(reset->sclk);
>> -        return ret;
>> +        goto unmap;
>>       }
>>         at91_reset_status(pdev, reset->rstc_base);
>>         return 0;
>> +
>> +unmap:
>> +    iounmap(reset->rstc_base);
>> +    for (idx = 0; idx < ARRAY_SIZE(reset->ramc_base); idx++)
>> +        iounmap(reset->ramc_base[idx]);
> 
> But if we keep this loop, I have the feeling that some kind of
> "of_node_put()" is needed as well.

No! In the loop:

for_each_matching_node_and_match(np, at91_ramc_of_match, &match) {
	reset->ramc_lpr = (u32)match->data;
	reset->ramc_base[idx] = of_iomap(np, 0);
	if (!reset->ramc_base[idx]) {
		dev_err(&pdev->dev, "Could not map ram controller address\n");
		of_node_put(np);
		ret = -ENODEV;
		goto unmap;
	}
	idx++;
}

the of_node_put() is needed only if the loop is interrupted as the macro:
for_each_matching_node_and_match() is defined as follows:

#define for_each_matching_node_and_match(dn, matches, match) \
	for (dn = of_find_matching_node_and_match(NULL, matches, match); \
	     dn; dn = of_find_matching_node_and_match(dn, matches, match))

and of_find_matching_node_and_match() will return a np with refcount
incremented but at the next loop step the of_find_matching_node_and_match()
will be called with the same np pointer and the np refcount will be
decremented.

struct device_node *of_find_matching_node_and_match(
		struct device_node *from,
		const struct of_device_id *matches,
		const struct of_device_id **match)
{
	// ...
	of_node_put(from);
	// ...
}

> 
>> +
>> +    return ret;
>>   }
>>     static int __exit at91_reset_remove(struct platform_device *pdev)
>>   {
>>       struct at91_reset *reset = platform_get_drvdata(pdev);
>> +    int idx;
>>         unregister_restart_handler(&reset->nb);
>>       clk_disable_unprepare(reset->sclk);
>>   +    iounmap(reset->rstc_base);
>> +    for (idx = 0; idx < ARRAY_SIZE(reset->ramc_base); idx++)
>> +        iounmap(reset->ramc_base[idx]);
> 
> Ditto
> 
>> +
>>       return 0;
>>   }
>>  
> 
>