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

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Message-ID: <DB7PR04MB4490EEEEF3E813A1EC34D1C68FA00@DB7PR04MB4490.eurprd04.prod.outlook.com>
Date:   Tue, 27 Aug 2019 08:12:12 +0000
From:   Biwen Li <biwen.li@....com>
To:     Nandor Han <nandor.han@...sala.com>,
        "a.zummo@...ertech.it" <a.zummo@...ertech.it>,
        "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>,
        Leo Li <leoyang.li@....com>,
        "broonie@...nel.org" <broonie@...nel.org>
CC:     "linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [EXT] 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
Thanks, it's a beautiful explanation.
> 
> Nandor