linux-kernel - Re: [PATCH] rtc: s5m: fix to update ctrl register

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Message-id: <55D6D24C.3010109@samsung.com>
Date:	Fri, 21 Aug 2015 16:25:00 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Joonyoung Shim <jy0922.shim@...sung.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Cc:	rtc-linux@...glegroups.com, linux-samsung-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	a.zummo@...ertech.it, sbkim73@...sung.com
Subject: Re: [PATCH] rtc: s5m: fix to update ctrl register

On 21.08.2015 15:58, Joonyoung Shim wrote:
> On 08/21/2015 10:21 AM, Krzysztof Kozlowski wrote:
>> On 21.08.2015 10:00, Joonyoung Shim wrote:
>>> On 08/21/2015 09:44 AM, Krzysztof Kozlowski wrote:
>>>> On 21.08.2015 08:15, Alexandre Belloni wrote:
>>>>> Hi,
>>>>>
>>>>> On 13/08/2015 at 17:49:24 +0900, Joonyoung Shim wrote :
>>>>>> According to datasheet, the S2MPS13X and S2MPS14X should update write
>>>>>> buffer via setting WUDR bit to high after ctrl register is updated.
>>>>>>
>>>>>> If not, ALARM interrupt of rtc-s5m doesn't happen first time when i use
>>>>>> tools/testing/selftests/timers/rtctest.c test program and hour format is
>>>>>> used to 12 hour mode in Odroid-XU3 board.
>>>>>>
>>>>>
>>>>> >From what I understood, I should expect a v2 of tihat patch also setting
>>>>> RUDR, is that right? OR would you prefer that I apply that one and then
>>>>> fix RUDR in a following patch?
>>>>
>>>> Right, I would expect that as well... or a comment if this is not needed.
>>>>
>>>
>>> Hmm, the driver only writes control register now, so i don't feel the
>>> need of patch setting RUDR for control register.
>>
>> Yes, you're right. There is only regmap_write() (not
>> remap_update_bits()) so your patch is completely fine. Thanks for
>> explanation.
>>
>> Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
>>
> 
> Thanks for review.
> 
> I found one more issue, the RTC doesn't keep time on Odroid-XU3 board
> when i turn on board after power off even if RTC battery is connected.
> 
> A difference with RTC driver of hardkernel kernel is that it sets
> not only WUDR bit but also RUDR bit to high at the same time after
> RTC_CTRL register is written. It's same with condition of only writing
> ALARM registers like below description.

It seems that setting RUDR to high is needed...  but it shouldn't. For
example in SM-G900H with S2MPS11 it is set before reading RTC_CTRL
register. Mainline driver does not perform read.

Maybe RUDR is not set high properly before some next time read and your
code is a coincidence, a work-around?

Best regards,
Krzysztof

> 
> from S2MPS14 datasheet:
> "3.  For write only Alarm 0&1 Registers (0x0B~0x18), set WUDR & RUDR
> bits to high."
> 
> So i tried it and it works well with keeping time. I'm not sure RTC of
> S2MPS13 type also has a similar issue because it differs a little bit.
> 
> from S2MPS13 datasheet:
> "3.  For write only Alarm 0&1 Registers (0x0B~0x18), set WUDR & A_UDR
> bits to high."
> 
> If S2MPS13 also has same issue, we can fix the problem via just below
> patch.
> 
> diff --git a/drivers/rtc/rtc-s5m.c b/drivers/rtc/rtc-s5m.c
> index 8c70d78..bb8e888 100644
> --- a/drivers/rtc/rtc-s5m.c
> +++ b/drivers/rtc/rtc-s5m.c
> @@ -635,6 +635,10 @@ static int s5m8767_rtc_init_reg(struct s5m_rtc_info *info)
>  	case S2MPS13X:
>  		data[0] = (0 << BCD_EN_SHIFT) | (1 << MODEL24_SHIFT);
>  		ret = regmap_write(info->regmap, info->regs->ctrl, data[0]);
> +		if (ret < 0)
> +			break;
> +
> +		ret = s5m8767_rtc_set_alarm_reg(info);
>  		break;
>  
>  	default:
> 
> But i can't find any reasonable reason about this fix from datasheet,
> 
> Thanks.
> 
>> Best regards,
>> Krzysztof
>>
>>>
>>>> Best regards,
>>>> Krzysztof
>>>>
>>>>
>>>>>
>>>>>> Signed-off-by: Joonyoung Shim <jy0922.shim@...sung.com>
>>>>>> Cc: <stable@...r.kernel.org>
>>>>>
>>>>> can you update the stable tag with the kernel version introducing the
>>>>> issue?
>>>
>>> Sure, i think it should be v3.16.
>>>
>>>>>
>>>>>> ---
>>>>>>  drivers/rtc/rtc-s5m.c | 12 ++++++++++++
>>>>>>  1 file changed, 12 insertions(+)
>>>>>
>>>>>> diff --git a/drivers/rtc/rtc-s5m.c b/drivers/rtc/rtc-s5m.c
>>>>>> index 8c70d78..03828bb 100644
>>>>>> --- a/drivers/rtc/rtc-s5m.c
>>>>>> +++ b/drivers/rtc/rtc-s5m.c
>>>>>> @@ -635,6 +635,18 @@ static int s5m8767_rtc_init_reg(struct s5m_rtc_info *info)
>>>>>>  	case S2MPS13X:
>>>>>>  		data[0] = (0 << BCD_EN_SHIFT) | (1 << MODEL24_SHIFT);
>>>>>>  		ret = regmap_write(info->regmap, info->regs->ctrl, data[0]);
>>>>>> +		if (ret < 0)
>>>>>> +			break;
>>>>>> +
>>>>>> +		ret = regmap_update_bits(info->regmap,
>>>>>> +				info->regs->rtc_udr_update,
>>>>>> +				info->regs->rtc_udr_mask,
>>>>>> +				info->regs->rtc_udr_mask);
>>>>>
>>>>> Very small indentation issue here, it should be aligned with the open
>>>>> parenthesis.
>>>
>>> OK, i will.
>>>
>>> Thanks.
>>>
>>
>>
> 
> 

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