[PATCH v3] iio: bu27034: Ensure reset is written

From: Matti Vaittinen
Date: Mon May 08 2023 - 07:03:17 EST

The reset bit must be always written to the hardware no matter what value
is in a cache or register. Ensure this by using regmap_write_bits()
instead of the regmap_update_bits(). Furthermore, the SWRESET bit may be
self-clearing, so mark the SYSTEM_CONTROL register volatile to guarantee
we do also read the right state - should we ever need to read it.

Finally, writing the SWRESET bit will restore the default register
values. This can cause register cache to be outdated if there are any
register values cached.

Rebuild register cache after SWRESET and use regmap_update_bits() when
performing the reset.

Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>
Fixes: e52afbd61039 ("iio: light: ROHM BU27034 Ambient Light Sensor")

v3: Combined patches:
("iio: bu27034: Ensure reset is written")
("iio: bu27034: Reinit regmap cache after reset")
drivers/iio/light/rohm-bu27034.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/light/rohm-bu27034.c b/drivers/iio/light/rohm-bu27034.c
index 25c9b79574a5..f85194fda6b0 100644
--- a/drivers/iio/light/rohm-bu27034.c
+++ b/drivers/iio/light/rohm-bu27034.c
@@ -231,6 +231,9 @@ struct bu27034_result {

static const struct regmap_range bu27034_volatile_ranges[] = {
+ .range_min = BU27034_REG_SYSTEM_CONTROL,
+ .range_max = BU27034_REG_SYSTEM_CONTROL,
+ }, {
.range_min = BU27034_REG_MODE_CONTROL4,
.range_max = BU27034_REG_MODE_CONTROL4,
}, {
@@ -1272,12 +1275,19 @@ static int bu27034_chip_init(struct bu27034_data *data)
int ret, sel;

/* Reset */
- ret = regmap_update_bits(data->regmap, BU27034_REG_SYSTEM_CONTROL,
+ ret = regmap_write_bits(data->regmap, BU27034_REG_SYSTEM_CONTROL,
if (ret)
return dev_err_probe(data->dev, ret, "Sensor reset failed\n");

+ ret = regmap_reinit_cache(data->regmap, &bu27034_regmap);
+ if (ret) {
+ dev_err(data->dev, "Failed to reinit reg cache\n");
+ return ret;
+ }
* Read integration time here to ensure it is in regmap cache. We do
* this to speed-up the int-time acquisition in the start of the buffer

Matti Vaittinen, Linux device drivers
ROHM Semiconductors, Finland SWDC
Kiviharjunlenkki 1E
90220 OULU

~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~
Simon says - in Latin please.
~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~
Thanks to Simon Glass for the translation =]

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