Re: [PATCH] iio: gyro: mpu3050: restore cached sample rate on runtime resume

[Andy Shevchenko]

On Fri, Jun 05, 2026 at 10:47:22AM +0200, Herman van Hazendonk wrote:
> mpu3050_runtime_resume() only calls mpu3050_power_up(), which clears
> the SLEEP bit and waits 200 ms for the chip's register file to come
> back. It does not reprogram the full-scale, low-pass filter or sample
> rate divisor, all of which return to the chip's power-on defaults
> across a power cycle.
> 
> The driver's cached state (mpu3050->fullscale, mpu3050->lpf,
> mpu3050->divisor) is the source of truth for what userspace observes
> through the IIO ABI: in_anglvel_sampling_frequency goes through
> mpu3050_get_freq() which reads the cached lpf and divisor, and
> in_anglvel_scale similarly reads cached fullscale. After the first
> autosuspend cycle the chip's actual sample rate diverges from what
> sysfs reports, until the next IIO_CHAN_INFO_RAW read incidentally
> reprograms the chip via mpu3050_set_8khz_samplerate() and the cached
> state restoration paths in mpu3050_fifo_read_one().
> 
> That incidental restoration is only triggered by direct sysfs raw
> reads, not by buffered/triggered mode. A user who configures the
> sample rate, starts buffered capture and then leaves the device idle
> long enough to autosuspend will see chip-default-rate samples after
> resume rather than the configured rate.
> 
> Reprogram the chip from the cached state in mpu3050_runtime_resume()
> by calling mpu3050_start_sampling() after mpu3050_power_up() succeeds.
> On failure power the chip back down to keep regulator and pm_runtime
> reference counts in sync with the error path.

The commit message (at least) looks like AI assisted. Is it true?

...

> +	/*
> +	 * mpu3050_power_up() only clears the SLEEP bit; it leaves the
> +	 * full-scale, low-pass filter and sample rate divisor at the
> +	 * chip's power-on defaults. Restore them from the driver's
> +	 * cached state so the hardware matches what userspace observes
> +	 * via the IIO ABI (in_anglvel_sampling_frequency, in_anglvel_scale)
> +	 * across a suspend/resume cycle. Without this the chip continues
> +	 * to deliver samples at chip-default rate after the first
> +	 * autosuspend cycle, until the next IIO_CHAN_INFO_RAW read
> +	 * incidentally reprograms it.
> +	 */
> +	ret = mpu3050_start_sampling(mpu3050);
> +	if (ret) {
> +		dev_err(dev, "failed to restore sampling config on resume\n");
> +		mpu3050_power_down(mpu3050);
> +		return ret;
> +	}
> +
> +	return 0;

Can be

	if (ret) {
		dev_err(dev, "failed to restore sampling config on resume\n");
		mpu3050_power_down(mpu3050);
	}

	return ret;

-- 
With Best Regards,
Andy Shevchenko