linux-kernel - Re: [v5] rtc: pcf85363/pcf85263: fix error that failed to run hwclock -w

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Date:   Thu, 29 Aug 2019 23:05:54 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Biwen Li <biwen.li@....com>
Cc:     a.zummo@...ertech.it, leoyang.li@....com, broonie@...nel.org,
        nandor.han@...sala.com, linux-rtc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [v5] rtc: pcf85363/pcf85263: fix error that failed to run
 hwclock -w

On 29/08/2019 10:14:18+0800, Biwen Li wrote:
> Issue:
>     - # hwclock -w
>       hwclock: RTC_SET_TIME: Invalid argument
> 
> Why:
>     - Relative commit: 8b9f9d4dc511309918c4f6793bae7387c0c638af, this patch
>       will always check for unwritable registers, it will compare reg
>       with max_register in regmap_writeable.
> 
>     - The pcf85363/pcf85263 has the capability of address wrapping
>       which means if you access an address outside the allowed range
>       (0x00-0x2f) hardware actually wraps the access to a lower address.
>       The rtc-pcf85363 driver will use this feature to configure the time
>       and execute 2 actions in the same i2c write operation (stopping the
>       clock and configure the time). However the driver has also
>       configured the `regmap maxregister` protection mechanism that will
>       block accessing addresses outside valid range (0x00-0x2f).
> 
> How:
>     - Split of writing regs to two parts, first part writes control
>       registers about stop_enable and resets, second part writes
>       RTC time and date registers.
> 
> Signed-off-by: Biwen Li <biwen.li@....com>
> ---
> Change in v5:
> 	- drop robust explanation
> 
> Change in v4:
> 	- use old scheme
> 	- replace link to lkml.org with commit
> 	- add proper explanation
> 
> Change in v3:
> 	- replace old scheme with new scheme:
> 	  increase max_register.
> 
> Change in v2:
> 	- add Why and How into commit message.
> 
>  drivers/rtc/rtc-pcf85363.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
Applied, thanks.

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