linux-kernel - Re: [PATCH] iio: adc: imx93_adc: load calibrated values even calibration failed

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Message-ID: <aAkYvE6VtoQItM5o@smile.fi.intel.com>
Date: Wed, 23 Apr 2025 19:43:40 +0300
From: Andy Shevchenko <andy@...nel.org>
To: Haibo Chen <haibo.chen@....com>
Cc: Jonathan Cameron <jic23@...nel.org>,
	David Lechner <dlechner@...libre.com>,
	Nuno Sá <nuno.sa@...log.com>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, linux-iio@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: adc: imx93_adc: load calibrated values even
 calibration failed

On Wed, Apr 23, 2025 at 04:02:48PM +0800, Haibo Chen wrote:
> ADC calibration might fail because of the noise on reference voltage.
> To avoid calibration fail, need to meet the following requirement:
> ADC reference voltage Noise < 1.8V * 1/2^ENOB
> 
> For the case which the ADC reference voltage on board do not meet
> the requirement, still load the calibrated values, so ADC can also
> work but maybe not that accurate.

...

>  #define IMX93_ADC_PCDR6		0x118
>  #define IMX93_ADC_PCDR7		0x11c
>  #define IMX93_ADC_CALSTAT	0x39C
> +#define IMX93_ADC_CALCFG0	0X3A0

Please, keep one style of the hex values.
If the small letters are less used, prepare a patch to convert them, otherwise
do that for capital letters.

...

> +	if (msr & IMX93_ADC_MSR_CALFAIL_MASK)

Please keep {} as the body is quite long and it's easy to make a mistake in a
long term.

> +		/*
> +		 * Only give warning here, this means the noise of the
> +		 * reference voltage do not meet the requirement:
> +		 *     ADC reference voltage Noise < 1.8V * 1/2^ENOB
> +		 * And the reault of ADC is not that accurate.
> +		 */
>  		dev_warn(adc->dev, "ADC calibration failed!\n");
> -		imx93_adc_power_down(adc);
> -		return -EAGAIN;
> -	}

-- 
With Best Regards,
Andy Shevchenko