linux-kernel - Re: [PATCH 3/7] reset: lpc18xx: use devm_reset_controller

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Message-ID: <CAK7LNAQ5LztGBbHCQxfLyWT7c_kWL=zpdKfkC9vsOKw95XL_Yw@mail.gmail.com>
Date:	Tue, 3 May 2016 00:52:18 +0900
From:	Masahiro Yamada <yamada.masahiro@...ionext.com>
To:	Philipp Zabel <p.zabel@...gutronix.de>
Cc:	Joachim Eastwood <manabian@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 3/7] reset: lpc18xx: use devm_reset_controller_register()

2016-05-02 17:26 GMT+09:00 Philipp Zabel <p.zabel@...gutronix.de>:
> Am Sonntag, den 01.05.2016, 19:36 +0900 schrieb Masahiro Yamada:
>> Use devm_reset_controller_register() for the reset controller
>> registration and remove the unregister call from the .remove callback.
>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
>> ---
>>
>>  drivers/reset/reset-lpc18xx.c | 4 +---
>>  1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/drivers/reset/reset-lpc18xx.c b/drivers/reset/reset-lpc18xx.c
>> index 3b8a4f5..dd4f27e 100644
>> --- a/drivers/reset/reset-lpc18xx.c
>> +++ b/drivers/reset/reset-lpc18xx.c
>> @@ -199,7 +199,7 @@ static int lpc18xx_rgu_probe(struct platform_device *pdev)
>>
>>       platform_set_drvdata(pdev, rc);
>>
>> -     ret = reset_controller_register(&rc->rcdev);
>> +     ret = devm_reset_controller_register(&pdev->dev, &rc->rcdev);
>>       if (ret) {
>>               dev_err(&pdev->dev, "unable to register device\n");
>>               goto dis_clks;
>> @@ -229,8 +229,6 @@ static int lpc18xx_rgu_remove(struct platform_device *pdev)
>>       if (ret)
>>               dev_warn(&pdev->dev, "failed to unregister restart handler\n");
>>
>> -     reset_controller_unregister(&rc->rcdev);
>> -
>>       clk_disable_unprepare(rc->clk_delay);
>>       clk_disable_unprepare(rc->clk_reg);
>>
>
> Hmm, would this patch theoretically allow a window between the calls to
> clk_disable_unprepare(clk_reg) and devm_reset_controller_release() where
> reset_control_get() + reset_control_(de)assert() would access unclocked
> registers?

This is not clear to me.

Why reset_control_get() + reset_control_(de)assert() would happen here?


devm_reset_controller_release() just calls reset_controller_unregister().

It is just a manipulation of a linked list.


void reset_controller_unregister(struct reset_controller_dev *rcdev)
{
      mutex_lock(&reset_controller_list_mutex);
      list_del(&rcdev->list);
      mutex_unlock(&reset_controller_list_mutex);
}




-- 
Best Regards
Masahiro Yamada