linux-kernel - Re: [v4] rtc: pcf85363/pcf85263: fix error that failed to run hwclock -w

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Message-ID: <2b49e282-fc03-ee59-2719-5a3c1ce573ce@vaisala.com>
Date:   Tue, 27 Aug 2019 11:07:24 +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: [v4] rtc: pcf85363/pcf85263: fix error that failed to run hwclock
 -w

On 8/27/19 7:37 AM, Biwen Li wrote:
>   - 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.
> 
>      - The pcf85363/pcf85263 has the capability of address wrapping
>        which means if you access a continuous address range across a
>        certain boundary(max_register of struct regmap_config) the
>        hardware actually wraps the access to a lower address. But the
>        address violation check of regmap rejects such access.

nitpick: This 2 paragraphs could be combined to clear up the issue:

`
The pcf85363/pcf85263 has the capability of address wrapping
which means if you access an address outside the allowed range 
(0x00-0x2f) the hardware actually wraps the access to a lower address. 
The rtc-pf85363 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).
`

nitpick: I would also use separate buffers for this actions. Up to you :)

Otherwise LGTM +1

Nandor