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

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

[Biwen Li]

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.

    - 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.

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@nxp.com>
---
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(-)

diff --git a/drivers/rtc/rtc-pcf85363.c b/drivers/rtc/rtc-pcf85363.c
index a075e77617dc..3450d615974d 100644
--- a/drivers/rtc/rtc-pcf85363.c
+++ b/drivers/rtc/rtc-pcf85363.c
@@ -166,7 +166,12 @@ static int pcf85363_rtc_set_time(struct device *dev, struct rtc_time *tm)
 	buf[DT_YEARS] = bin2bcd(tm->tm_year % 100);
 
 	ret = regmap_bulk_write(pcf85363->regmap, CTRL_STOP_EN,
-				tmp, sizeof(tmp));
+				tmp, 2);
+	if (ret)
+		return ret;
+
+	ret = regmap_bulk_write(pcf85363->regmap, DT_100THS,
+				buf, sizeof(tmp) - 2);
 	if (ret)
 		return ret;
 
-- 
2.17.1

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

[Nandor Han]

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

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

[Biwen Li]

> 
> 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