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

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Message-ID: <65a85fb2-0482-2007-4a84-b622e5308c3d@vaisala.com>
Date:   Thu, 29 Aug 2019 09:45:50 +0300
From:   Nandor Han <nandor.han@...sala.com>
To:     Biwen Li <biwen.li@....com>, a.zummo@...ertech.it,
        alexandre.belloni@...tlin.com, leoyang.li@....com,
        broonie@...nel.org
Cc:     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 8/29/19 5:14 AM, 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
> 

LGTM +1

Nandor