[PATCH AUTOSEL 4.19 15/33] rtc: pcf85363/pcf85263: fix regmap error in set_time

[Sasha Levin]

From: Biwen Li <biwen.li@xxxxxxx>

[ Upstream commit 7ef66122bdb3b839e9f51b76d7e600b6e21ef648 ]

Issue:
    - # hwclock -w
      hwclock: RTC_SET_TIME: Invalid argument

Why:
    - Relative commit: 8b9f9d4dc511 ("regmap: verify if register is
      writeable before writing operations"), 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@xxxxxxx>
Link: https://lore.kernel.org/r/20190829021418.4607-1-biwen.li@xxxxxxx
Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 c04a1edcd5716..c3702684b3426 100644
--- a/drivers/rtc/rtc-pcf85363.c
+++ b/drivers/rtc/rtc-pcf85363.c
@@ -169,7 +169,12 @@ 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;
 
-- 
2.20.1