Re: [PROBLEM]: Error during probing process in inv_icm42600_i2c driver

[Jean-Baptiste Maneyrol <Jean-Baptiste.Maneyrol@tdk.com>]

Hello,

this is a known issue. When setting I2C parameters, it enables some specific filter for improving transfer quality. These filters are by default disabled to enable I3C usage.

This operation creates a spike in the lines that make the transaction fails even if it is in fact doing OK.

Do not change the register value. The fix is to ignore the return value of the regmap_update_bits done on INV_ICM42600_REG_INTF_CONFIG6.

If you want to create a patch, it would be very welcomed I could review it.

Thanks,
JB


From: Jonathan Cameron <jic23@kernel.org>
Sent: Sunday, January 30, 2022 16:17
To: Nikos Latmos <n.latmos@deepsea.ai>
Cc: jmaneyrol@invensense.com <jmaneyrol@invensense.com>; lars@metafoo.de <lars@metafoo.de>; linux-iio@vger.kernel.org <linux-iio@vger.kernel.org>; linux-kernel@vger.kernel.org <linux-kernel@vger.kernel.org>
Subject: Re: [PROBLEM]: Error during probing process in inv_icm42600_i2c driver 
 
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On Wed, 8 Dec 2021 16:33:52 +0200
Nikos Latmos <n.latmos@deepsea.ai> wrote:

> Hello,
> 
> I have an ARM device based on the Broadcom BCM2837 processor (quad-core
> ARM Cortex-A53, 1.2GHz), which has an Invensense ICM-42605 IMU chip
> connected over I2C. I'm running an unmodified Linux 5.4.83 kernel. The I2C
> driver for my device is in the following path:
> drivers/iio/imu/inv_icm42600/inv_icm42600_i2c.c.
> 
> The problem is that the device driver cannot be probed. More specifically,
> dmesg returns the following error message:
> 
> inv-icm42600-i2c 0-0068: mounting matrix not found: using identity...
> inv-icm42600-i2c 0-0068: 0-0068 supply vdd not found, using dummy regulator
> inv-icm42600-i2c 0-0068: 0-0068 supply vddio not found, using dummy regulator
> inv-icm42600-i2c: probe of 0-0068 failed with error -121
> 
> During the debugging procedure, I found out that the failure occurred when
> the driver tried to set up the I2C bus parameters. More precisely, by setting
> the INV_ICM42600_REG_INTF_CONFIG6 register according to the values described
> in the datasheet for the I2C communication, actually caused the probe function
> to fail and return the error -121.
> 
> After I experimented with different values in the specific register bits,
> I came to the conclusion, that the setting of the bit
> INV_ICM42600_INTF_CONFIG6_I3C_SDR_EN caused the system to successfully
> probe the driver. Any other bit setting combinations failed to do so.
> 
> Any hints on why would the driver behave so?
> 
> Here is a patch that I have so far and it seems to solve the issue.
> 
> Best regards,
> Nick Latmos

Hi All,

Anyone familiar with this part able to help Nick?

Thanks,

Jonathan

> 
> 
> From d7b3922cd0182ba880ff729edb4a156b55dfb6f0 Mon Sep 17 00:00:00 2001
> From: nicklat <n.latmos@deepsea.ai>
> Date: Wed, 8 Dec 2021 15:51:28 +0200
> Subject: [PATCH] iio: imu: inv_icm42600: enable SDR mode
> 
> Add SDR (Single Data Rate) support.
> In SDR mode, data is only clocked on one edge of the clock.
> 
> Without this option enabled, the probing process fails.
> 
> Signed-off-by: nicklat <n.latmos@deepsea.ai>
> ---
>  drivers/iio/imu/inv_icm42600/inv_icm42600_i2c.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/imu/inv_icm42600/inv_icm42600_i2c.c
> b/drivers/iio/imu/inv_icm42600/inv_icm42600_i2c.c
> index 85b1934cec60..ea31f102fbca 100644
> --- a/drivers/iio/imu/inv_icm42600/inv_icm42600_i2c.c
> +++ b/drivers/iio/imu/inv_icm42600/inv_icm42600_i2c.c
> @@ -21,7 +21,8 @@ static int inv_icm42600_i2c_bus_setup(struct
> inv_icm42600_state *st)
>         /* setup interface registers */
>         ret = regmap_update_bits(st->map, INV_ICM42600_REG_INTF_CONFIG6,
>                                  INV_ICM42600_INTF_CONFIG6_MASK,
> -                                INV_ICM42600_INTF_CONFIG6_I3C_EN);
> +                                INV_ICM42600_INTF_CONFIG6_I3C_EN |
> +                                INV_ICM42600_INTF_CONFIG6_I3C_SDR_EN);
>         if (ret)
>                 return ret;
> 
> --
> 2.25.1