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SubjectRe: [EXT] Re: [v2] rtc: pcf85363/pcf85263: fix error that failed to run hwclock -w
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On 8/26/19 7:29 AM, Biwen Li wrote:
>>
>> On 8/16/19 10:40 PM, Li Yang wrote:
>>> On Fri, Aug 16, 2019 at 11:30 AM Alexandre Belloni
>>> <alexandre.belloni@bootlin.com> wrote:
>>>>
>>>> On 16/08/2019 10:50:49-0500, Li Yang wrote:
>>>>> On Fri, Aug 16, 2019 at 3:05 AM Alexandre Belloni
>>>>> <alexandre.belloni@bootlin.com> wrote:
>>>>>>
>>>>>> On 16/08/2019 10:46:36+0800, Biwen Li wrote:
>>>>>>> Issue:
>>>>>>> - # hwclock -w
>>>>>>> hwclock: RTC_SET_TIME: Invalid argument
>>>>>>>
>>>>>>> Why:
>>>>>>> - Relative patch:
>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flkml.org
>> %2Flkml%2F2019%2F4%2F3%2F55&amp;data=02%7C01%7Cbiwen.li%40nxp.
>> com%7Cff8cebc3f1034ae3fa9608d725ff9e5e%7C686ea1d3bc2b4c6fa92cd99
>> c5c301635%7C0%7C0%7C637019652111923736&amp;sdata=spY6e22YOkOF
>> 3%2BF7crSM0M6xPmOhgULDqMZLQw%2BAmdI%3D&amp;reserved=0 , this
>> patch
>>>>>>> will always check for unwritable registers, it will compare reg
>>>>>>> with max_register in regmap_writeable.
>>>>>>>
>>>>>>> - In drivers/rtc/rtc-pcf85363.c, CTRL_STOP_EN is 0x2e, but
>> DT_100THS
>>>>>>> is 0, max_regiter is 0x2f, then reg will be equal to 0x30,
>>>>>>> '0x30 < 0x2f' is false,so regmap_writeable will return false.
>>>>>>>
>>>>>>> - Root cause: the buf[] was written to a wrong place in the file
>>>>>>> drivers/rtc/rtc-pcf85363.c
>>>>>>>
>>>>>>
>>>>>> This is not true, the RTC wraps the register accesses properly and
>>>>>> this
>>>>>
>>>>> This performance hack probably deserve some explanation in the code
>>>>> comment. :)
>>>>>
>>>>>> is probably something that should be handled by regmap_writable.
>>>>>
>>>>> The address wrapping is specific to this RTC chip. Is it also
>>>>> commonly used by other I2C devices? I'm not sure if regmap_writable
>>>>> should handle the wrapping case if it is too special.
>>>>>
>>>>
>>>> Most of the i2c RTCs do address wrapping which is sometimes the only
>>>> way to properly set the time.
>>>
>>> Adding Mark and Nandor to the loop.
>>>
>>> Regards,
>>> Leo
>>>
>>
>> Hi,
>> `regmap` provides couple of ways to validate the registers:
>> max_register, callback function and write table. All of these are optional, so it
>> gives you the freedom to customize it as needed.
>>
>> In this situation probably you could:
>> 1. Avoid using the wrapping feature of pcf85363 (you can just provide
>> separate calls for stop, reset and time confguration). In this way the
>> `max_register` validation method will work fine.
> Yes, I use this way. Path as follows:
> Stop and reset - > set time > stop
>

Some of the concerns regarding this method was that it might not be
precise enough. That because you need 2 I2C operations (one for stop and
one for time configuration). Not sure about your case if this is a
problem or not.

>> 2. Replace `max_register` method validation with `callback function`
>> validation method, were you could make your own validation.
> It is not work, show the code in as follows:
>
> bool regmap_writeable(struct regmap *map, unsigned int reg)
> {
> if (map->max_register && reg > map->max_register)
> return false;
> Callback function (writeable_reg) will not be called.
> if (map->writeable_reg)
> return map->writeable_reg(map->dev, reg);

Hi Li,
If you *replace* the `max_register` method with `callback function`
it should work. The code above will use every method *if provided*. In
other words if `map->max_register` is 0 will go to the next step and
check `map->writeable_reg`. Right?



Regards,
Nandor

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