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

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Message-ID: <5fbc077d-1f45-6bc0-8d73-6008c6a28e76@microchip.com>
Date:   Thu, 1 Apr 2021 14:50:14 +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 01.04.2021 17:42, Claudiu Beznea - M18063 wrote:
> 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

Just realized I looked at the wrong code. Anyway, I'll double check and return.

> 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;
>>>   }
>>>  
>>
>>
>