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

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Message-id: <55D6CC1C.9040402@samsung.com>
Date:	Fri, 21 Aug 2015 15:58:36 +0900
From:	Joonyoung Shim <jy0922.shim@...sung.com>
To:	Krzysztof Kozlowski <k.kozlowski@...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 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.

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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