linux-kernel - Re: [RFC PATCH 1/2] rtc: s3c: Remove unnecessary call to disable already disabled clock

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 05 Jul 2016 14:16:54 +0530
From:	Alim Akhtar <alim.akhtar@...sung.com>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org
Cc:	alexandre.belloni@...e-electrons.com, javier@....samsung.com,
	pankaj.dubey@...sung.com
Subject: Re: [RFC PATCH 1/2] rtc: s3c: Remove unnecessary call to disable
 already disabled clock

Hi Krzsztof,

On 07/05/2016 12:48 PM, Krzysztof Kozlowski wrote:
> On 07/04/2016 01:03 PM, Alim Akhtar wrote:
>> At the end of s3c_rtc_probe(), s3c_rtc_disable_clk() being called with rtc
>> clock already disabled, which looks extra and unnecessary call.
>> Lets clean it up.
>
> Does not look right. Till that place, the clocks are enabled. Then
> s3c_rtc_setaie() is called which expects that clocks are disabled...
> otherwise counters get mixed.
>

The clock is always disabled when it reach s3c_rtc_setfreq() in probe(),
because s3c_rtc_gettime() will always disable the clock.

As far as s3c_rtc_setaie() is concern, it enables clock while entering 
and disables it while leaving the function. And in 
s3c_rtc_{enable,disable}_clk() there is check info->clk_disabled flag 
which will make sure clock balancing.

> So overall this looks like wrong approach unless I am missing something?
>
> Best regards,
> Krzysztof
>
>>
>> Signed-off-by: Alim Akhtar <alim.akhtar@...sung.com>
>> ---
>>   drivers/rtc/rtc-s3c.c |    2 --
>>   1 file changed, 2 deletions(-)
>>
>> diff --git a/drivers/rtc/rtc-s3c.c b/drivers/rtc/rtc-s3c.c
>> index d01ad7e..b083840 100644
>> --- a/drivers/rtc/rtc-s3c.c
>> +++ b/drivers/rtc/rtc-s3c.c
>> @@ -577,8 +577,6 @@ static int s3c_rtc_probe(struct platform_device *pdev)
>>
>>   	s3c_rtc_setfreq(info, 1);
>>
>> -	s3c_rtc_disable_clk(info);
>> -
>>   	return 0;
>>
>>    err_nortc:
>
>