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

[Nandor Han]

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://lkml.org/lkml/2019/4/3/55 , 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.
  2. Replace `max_register` method validation with `callback function` 
validation method, were you could make your own validation.


Regards,
   Nandor