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Date:   Sun, 30 Jan 2022 15:17:37 +0000
From:   Jonathan Cameron <jic23@kernel.org>
To:     Nikos Latmos <n.latmos@deepsea.ai>
Cc:     jmaneyrol@invensense.com, lars@metafoo.de,
        linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PROBLEM]: Error during probing process in inv_icm42600_i2c
 driver
Message-ID: <20220130151737.43ef5b08@jic23-huawei>
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References: <20211208135644.3523024-1-n.latmos@deepsea.ai>
        <CAC-bbXbkt0oYPn+EWLdEYKyj8G_muWGDZWTApyFv3cb591dc0A@mail.gmail.com>
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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