Re: [EXT] Re: [v2] rtc: pcf85363/pcf85263: fix error that failed to run hwclock -w

[Nandor Han]

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@xxxxxxxxxxx> 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@xxxxxxxxxxx> 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