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. -- Alexandre Belloni, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
