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

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Date:   Fri, 16 Aug 2019 10:04:17 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Biwen Li <biwen.li@....com>
Cc:     a.zummo@...ertech.it, leoyang.li@....com,
        linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [v2] rtc: pcf85363/pcf85263: fix error that failed to run
 hwclock -w

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
is probably something that should be handled by regmap_writable.

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