Re: [PATCH v5 1/3] iio: adc: add imx93 adc support

[Jonathan Cameron <jic23@kernel.org>]

On Tue,  3 Jan 2023 19:43:56 +0800
haibo.chen@nxp.com wrote:

> From: Haibo Chen <haibo.chen@nxp.com>
> 
> The ADC in i.mx93 is a total new ADC IP, add a driver to support
> this ADC.
> 
> Currently, only support one shot normal conversion triggered by
> software. For other mode, will add in future.
> 
> Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Hi Haibo,

I'm still not sure about the power handling in remove. One other
minor comment inline that would be good to clean up for v6.

Thanks,

Jonathan

> new file mode 100644
> index 000000000000..0c98de438919
> --- /dev/null
> +++ b/drivers/iio/adc/imx93_adc.c

...

> +
> +static int imx93_adc_calibration(struct imx93_adc *adc)
> +{
> +	u32 mcr, msr;
> +	int ret;
> +
> +	/* make sure ADC in power down mode */
> +	imx93_adc_power_down(adc);
> +
> +	/* config SAR controller operating clock */
> +	mcr = readl(adc->regs + IMX93_ADC_MCR);
> +	mcr &= ~FIELD_PREP(IMX93_ADC_MCR_ADCLKSE_MASK, 1);
> +	writel(mcr, adc->regs + IMX93_ADC_MCR);
> +
> +	imx93_adc_power_up(adc);

I think this function should be side effect free on error to aid easy reviewing
/ code modularity. Thus if anything after this point fails, the device
should be deliberately powered down again to remove that side effect.

> +
> +	/*
> +	 * TODO: we use the default TSAMP/NRSMPL/AVGEN in MCR,
> +	 * can add the setting of these bit if need in future.
> +	 */
> +
> +	/* run calibration */
> +	mcr = readl(adc->regs + IMX93_ADC_MCR);
> +	mcr |= FIELD_PREP(IMX93_ADC_MCR_CALSTART_MASK, 1);
> +	writel(mcr, adc->regs + IMX93_ADC_MCR);
> +
> +	/* wait calibration to be finished */
> +	ret = readl_poll_timeout(adc->regs + IMX93_ADC_MSR, msr,
> +		!(msr & IMX93_ADC_MSR_CALBUSY_MASK), 1000, 2000000);
> +	if (ret == -ETIMEDOUT) {
> +		dev_warn(adc->dev, "ADC do not finish calibration in 1 min!\n");
> +		return ret;
> +	}
> +
> +	/* check whether calbration is success or not */
> +	msr = readl(adc->regs + IMX93_ADC_MSR);
> +	if (msr & IMX93_ADC_MSR_CALFAIL_MASK) {
> +		dev_warn(adc->dev, "ADC calibration failed!\n");
> +		return -EAGAIN;
> +	}
> +
> +	return 0;
> +}
> +

...

> +static int imx93_adc_probe(struct platform_device *pdev)
> +{
> +	struct imx93_adc *adc;
> +	struct iio_dev *indio_dev;
> +	struct device *dev = &pdev->dev;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
> +	if (!indio_dev)
> +		return dev_err_probe(dev, -ENOMEM,
> +				     "Failed allocating iio device\n");
> +
> +	adc = iio_priv(indio_dev);
> +	adc->dev = dev;
> +
> +	mutex_init(&adc->lock);
> +	adc->regs = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(adc->regs))
> +		return dev_err_probe(dev, PTR_ERR(adc->regs),
> +				     "Failed geting ioremap resource\n");
> +
> +	/* The third irq is for ADC conversion usage */
> +	adc->irq = platform_get_irq(pdev, 2);
> +	if (adc->irq < 0)
> +		return adc->irq;
> +
> +	adc->ipg_clk = devm_clk_get(dev, "ipg");
> +	if (IS_ERR(adc->ipg_clk))
> +		return dev_err_probe(dev, PTR_ERR(adc->ipg_clk),
> +				     "Failed getting clock.\n");
> +
> +	adc->vref = devm_regulator_get(dev, "vref");
> +	if (IS_ERR(adc->vref))
> +		return dev_err_probe(dev, PTR_ERR(adc->vref),
> +				     "Failed getting reference voltage.\n");
> +
> +	ret = regulator_enable(adc->vref);
> +	if (ret)
> +		return dev_err_probe(dev, ret,
> +				     "Failed to enable reference voltage.\n");
> +
> +	platform_set_drvdata(pdev, indio_dev);
> +
> +	init_completion(&adc->completion);
> +
> +	indio_dev->name = "imx93-adc";
> +	indio_dev->info = &imx93_adc_iio_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->channels = imx93_adc_iio_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(imx93_adc_iio_channels);
> +
> +	ret = clk_prepare_enable(adc->ipg_clk);
> +	if (ret) {
> +		dev_err_probe(dev, ret,
> +			      "Failed to enable ipg clock.\n");
> +		goto error_regulator_disable;
> +	}
> +
> +	ret = request_irq(adc->irq, imx93_adc_isr, 0, IMX93_ADC_DRIVER_NAME, adc);
> +	if (ret < 0) {
> +		dev_err_probe(dev, ret,
> +			      "Failed requesting irq, irq = %d\n", adc->irq);
> +		goto error_ipg_clk_disable;
> +	}
> +
> +	ret = imx93_adc_calibration(adc);
> +	if (ret < 0)

As above, I'd expect the device to be powered down if this function fails
and hence need an additional error label.

> +		goto error_free_adc_irq;
> +
> +	imx93_adc_config_ad_clk(adc);
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret) {
> +		dev_err_probe(dev, ret,
> +			      "Failed to register this iio device.\n");
> +		goto error_free_adc_irq;
> +	}
> +
> +	pm_runtime_set_active(dev);
> +	pm_runtime_set_autosuspend_delay(dev, 50);
> +	pm_runtime_use_autosuspend(dev);
> +	pm_runtime_enable(dev);
> +
> +	return 0;
> +
> +error_free_adc_irq:
> +	imx93_adc_power_down(adc);
> +	free_irq(adc->irq, adc);
> +error_ipg_clk_disable:
> +	clk_disable_unprepare(adc->ipg_clk);
> +error_regulator_disable:
> +	regulator_disable(adc->vref);
> +
> +	return ret;
> +}
> +
> +static int imx93_adc_remove(struct platform_device *pdev)
> +{
> +	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> +	struct imx93_adc *adc = iio_priv(indio_dev);
> +	struct device *dev = adc->dev;

As per reply to cover letter I don't understand logic by which we
are definitely runtime resumed at this stage.

> +
> +	pm_runtime_disable(dev);
> +	pm_runtime_dont_use_autosuspend(dev);
> +	pm_runtime_put_noidle(dev);

This is not balanced with a pm_runtime_get* so I think we underflow
(which is protected against in runtime pm ref counting but not a nice
thing to do deliberately).

> +	iio_device_unregister(indio_dev);
> +	imx93_adc_power_down(adc);
> +	free_irq(adc->irq, adc);
> +	clk_disable_unprepare(adc->ipg_clk);
> +	regulator_disable(adc->vref);
> +
> +	return 0;
> +}
> +