[PATCH 2/2] thermal: imx91: Add support for i.MX91 thermal monitoring unit

[Marco Felsch]

On 24-12-10, Frank Li wrote:
> On Tue, Dec 10, 2024 at 11:36:46AM +0100, Marco Felsch wrote:
> > Hi,
> >
> > On 24-12-09, Frank Li wrote:

...

> > > +	/* disable the monitor during initialization */
> > > +	imx91_tmu_enable(tmu, false);
> > > +	imx91_tmu_start(tmu, false);
> >
> > Make use of pm_runtime?
> 
> thermal is always on after probe. continue measure tempature. So pm_runtime
> is not suitable for this case.

There are at least 3 drivers which use pm-runtime including the i.MX6/7
imx_thermal.c driver.

> > > +	ret = imx91_init_from_nvmem_cells(tmu);
> > > +	if (ret) {
> > > +		writel_relaxed(DEFAULT_TRIM1_CONFIG, tmu->base + TRIM1);
> > > +		writel_relaxed(DEFAULT_TRIM2_CONFIG, tmu->base + TRIM2);
> > > +	}
> > > +
> > > +	/* The typical conv clk is 4MHz, the output freq is 'rate / (div + 1)' */
> > > +	rate = clk_get_rate(tmu->clk);
> > > +	div = (rate / 4000000) - 1;
> >
> > Would be nice to validate the div value before passing to the HW and if
> > the target rate of 4MHz can't be reached by the div you you should
> > return -EINVAL.
> >
> > > +
> > > +	/* Set divider value and enable divider */
> > > +	writel_relaxed(DIV_EN | FIELD_PREP(DIV_MASK, div), tmu->base + REF_DIV);
> > > +
> > > +	/* Set max power up delay: 'Tpud(ms) = 0xFF * 1000 / 4000000' */
> > > +	writel_relaxed(FIELD_PREP(PUDL_MASK, 100U), tmu->base + PUD_ST_CTRL);
> > > +
> > > +	/*
> > > +	 * Set resolution mode
> > > +	 * 00b - Conversion time = 0.59325 ms
> > > +	 * 01b - Conversion time = 1.10525 ms
> > > +	 * 10b - Conversion time = 2.12925 ms
> > > +	 * 11b - Conversion time = 4.17725 ms
> > > +	 */
> > > +	writel_relaxed(FIELD_PREP(CTRL1_RES_MASK, 0x3), tmu->base + CTRL1_CLR);
> > > +	writel_relaxed(FIELD_PREP(CTRL1_RES_MASK, 0x1), tmu->base + CTRL1_SET);
> > > +
> > > +	/*
> > > +	 * Set measure mode
> > > +	 * 00b - Single oneshot measurement
> > > +	 * 01b - Continuous measurement
> > > +	 * 10b - Periodic oneshot measurement
> > > +	 */
> >
> > For the resolution it's fine to have the values directly coded without a
> > define, but here we can definitly use a define and drop the comment.
> >
> > > +	writel_relaxed(FIELD_PREP(CTRL1_MEAS_MODE_MASK, 0x3), tmu->base + CTRL1_CLR);
> > > +	writel_relaxed(FIELD_PREP(CTRL1_MEAS_MODE_MASK, 0x1), tmu->base + CTRL1_SET);
> >
> > Why do we set it to periodic mode instead of the single-shot? At the
> > moment the device doesn't have IRQ support, and so there is no need to
> > run the measurements in background.
> 
> It is "continous measurement".  first clean MODE_MASK, then then 01.

Still, why? You return the temp value upon a request (get_temp). There
is no async notification from this driver to others. So it can be left
to single-shot and do the measurement on request (get_temp).

> _CLR means clean bits according to mask
> _SET means set bits according to mask.

I know.

Regards,
  Marco

> 
> Frank
> 
> >
> > > +
> > > +	/*
> > > +	 * Set Periodic Measurement Frequency to 25Hz:
> > > +	 * tMEAS_FREQ = tCONV_CLK * PERIOD_CTRL[MEAS_FREQ]. ->
> > > +	 * PERIOD_CTRL(MEAS_FREQ) = (1000 / 25) / (1000 / 4000000);
> > > +	 * Where tMEAS_FREQ = Measurement period and tCONV_CLK = 1/fCONV_CLK.
> > > +	 * This field should have value greater than count corresponds
> > > +	 * to time greater than summation of conversion time, power up
> > > +	 * delay, and six times of conversion clock time.
> > > +	 * tMEAS_FREQ > (tCONV + tPUD + 6 * tCONV_CLK).
> > > +	 * tCONV is conversion time determined by CTRL1[RESOLUTION].
> > > +	 */
> > > +	writel_relaxed(FIELD_PREP(MEAS_FREQ_MASK, 0x27100), tmu->base + PERIOD_CTRL);
> >
> > With the single-shot measurements we could remove this part and..
> >
> > > +
> > > +	/* enable the monitor */
> > > +	imx91_tmu_enable(tmu, true);
> > > +	imx91_tmu_start(tmu, true);
> >
> > this part as well.
> >
> > Regards,
> >   Marco
> >
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static void imx91_tmu_remove(struct platform_device *pdev)
> > > +{
> > > +	struct imx91_tmu *tmu = platform_get_drvdata(pdev);
> > > +
> > > +	/* disable tmu */
> > > +	imx91_tmu_start(tmu, false);
> > > +	imx91_tmu_enable(tmu, false);
> > > +}
> > > +
> > > +static int __maybe_unused imx91_tmu_suspend(struct device *dev)
> > > +{
> > > +	struct imx91_tmu *tmu = dev_get_drvdata(dev);
> > > +
> > > +	/* disable tmu */
> > > +	imx91_tmu_start(tmu, false);
> > > +	imx91_tmu_enable(tmu, false);
> > > +
> > > +	clk_disable_unprepare(tmu->clk);
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static int __maybe_unused imx91_tmu_resume(struct device *dev)
> > > +{
> > > +	struct imx91_tmu *tmu = dev_get_drvdata(dev);
> > > +	int ret;
> > > +
> > > +	ret = clk_prepare_enable(tmu->clk);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	imx91_tmu_enable(tmu, true);
> > > +	imx91_tmu_start(tmu, true);
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static SIMPLE_DEV_PM_OPS(imx91_tmu_pm_ops,
> > > +			 imx91_tmu_suspend, imx91_tmu_resume);
> > > +
> > > +static const struct of_device_id imx91_tmu_table[] = {
> > > +	{ .compatible = "fsl,imx91-tmu", },
> > > +	{ },
> > > +};
> > > +MODULE_DEVICE_TABLE(of, imx91_tmu_table);
> > > +
> > > +static struct platform_driver imx91_tmu = {
> > > +	.driver = {
> > > +		.name	= "i.MX91_thermal",
> > > +		.pm	= pm_ptr(&imx91_tmu_pm_ops),
> > > +		.of_match_table = imx91_tmu_table,
> > > +	},
> > > +	.probe = imx91_tmu_probe,
> > > +	.remove = imx91_tmu_remove,
> > > +};
> > > +module_platform_driver(imx91_tmu);
> > > +
> > > +MODULE_AUTHOR("Peng Fan <peng.fan at nxp.com>");
> > > +MODULE_DESCRIPTION("i.MX91 Thermal Monitor Unit driver");
> > > +MODULE_LICENSE("GPL");
> > >
> > > --
> > > 2.34.1
> > >
> > >
> > >
>