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 RESET 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.
Signed-off by: Matti Vaittinen <[email protected]>
Fixes: e52afbd61039 ("iio: light: ROHM BU27034 Ambient Light Sensor")
---
I haven't verified if the reset bit is self-clearin as I did temporarily
give away the HW.
In worst case the bit is not self clearing - but we don't really
get performance penalty even if we set the register volatile because the
SYSTEM_CONTROL register only has the part-ID and the reset fields. The
part-ID is only read once at probe.
---
drivers/iio/light/rohm-bu27034.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/iio/light/rohm-bu27034.c b/drivers/iio/light/rohm-bu27034.c
index 25c9b79574a5..740ebd86b6e5 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,
}, {
@@ -1272,7 +1275,7 @@ 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,
BU27034_MASK_SW_RESET, BU27034_MASK_SW_RESET);
if (ret)
return dev_err_probe(data->dev, ret, "Sensor reset failed\n");
base-commit: 7fcbd72176076c44b47e8f68f0223c02c411f420
--
2.40.0
--
Matti Vaittinen, Linux device drivers
ROHM Semiconductors, Finland SWDC
Kiviharjunlenkki 1E
90220 OULU
FINLAND
~~~ "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 =]
On 5/2/23 19:00, Matti Vaittinen wrote:
> 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 RESET 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.
>
> Signed-off by: Matti Vaittinen <[email protected]>
I misspelled the Signed-off-by. Sorry folks. I'll re-spin.
Yours,
-- Matti
--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland
~~ When things go utterly wrong vim users can always type :help! ~~