Re: [PATCH V5 04/11] iio: imu: inv_icm42607: Add I2C and SPI For icm42607

[Jonathan Cameron <jic23@kernel.org>]

On Sat,  9 May 2026 14:18:58 -0500
Chris Morgan <macroalpha82@gmail.com> wrote:

> From: Chris Morgan <macromorgan@hotmail.com>
> 
> Add I2C and SPI driver support for InvenSense ICM-42607 devices.
> Add necessary Kconfig and Makefile to allow building of (incomplete)
> driver.
> 
> Signed-off-by: Chris Morgan <macromorgan@hotmail.com>

Sashiko got busy and found something that I now realize I didn't
understand at all :(


> diff --git a/drivers/iio/imu/inv_icm42607/inv_icm42607_core.c b/drivers/iio/imu/inv_icm42607/inv_icm42607_core.c
> index e84e84416dab..8ff51711ab1f 100644
> --- a/drivers/iio/imu/inv_icm42607/inv_icm42607_core.c
> +++ b/drivers/iio/imu/inv_icm42607/inv_icm42607_core.c
> @@ -15,6 +15,57 @@
>  
>  #include "inv_icm42607.h"
>  
> +static const struct regmap_range_cfg inv_icm42607_regmap_ranges[] = {
> +	{
> +		.name = "user bank",
> +		.range_min = 0x0000,
> +		.range_max = 0x00FF,
> +		.window_start = 0,
> +		.window_len = 0x0100,

I'd never really looked at this bit of regmap before but sashiko
did suggest a possible issue and from the documentation it appears it
might be right. 
 * Registers, mapped to this virtual range, are accessed in two steps:
 *     1. page selector register update;
 *     2. access through data window registers.

So whether or not we want one the page selector infrastructure is
used.

So Sashiko suggested we'll get a bank setting write to register 0
with value 0.

Having dug around I found a 42607-c datasheet:
https://www.lcsc.com/datasheet/C2879807.pdf?spm=wm.sxq.inf.ggs&lcsc_vid=EVNXBlQAR1RZAwIHTwMLUVcEFgVcAQdQQgVeBlJSQAIxVlNRT1RcVldeQlZeVzsOAxUeFF5JWBYZEEoBGA4JCwFIFA4DSA%3D%3D

That suggests there is a bank select register but at 0x7c which isn't
documented for the 42607P :(

It also doesn't correspond to conventional window / bank arrangement so
this probably doesn't apply anyway.


> +	},
> +};
> +
> +const struct regmap_config inv_icm42607_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +	.max_register = 0x00FF,
> +	.ranges = inv_icm42607_regmap_ranges,
> +	.num_ranges = ARRAY_SIZE(inv_icm42607_regmap_ranges),
> +	.cache_type = REGCACHE_NONE,
> +};
> +EXPORT_SYMBOL_NS_GPL(inv_icm42607_regmap_config, "IIO_ICM42607");