linux-kernel - Re: [PATCH v3] iio: adc: spear_adc: mask SPEAR_ADC_STATUS channel and avg sample before setting register

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Message-ID: <20250719131039.07a5fb24@jic23-huawei>
Date: Sat, 19 Jul 2025 13:10:39 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Rodrigo Gobbi <rodrigo.gobbi.7@...il.com>
Cc: dlechner@...libre.com, nuno.sa@...log.com, andy@...nel.org,
 ~lkcamp/patches@...ts.sr.ht, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] iio: adc: spear_adc: mask SPEAR_ADC_STATUS channel
 and avg sample before setting register

On Thu, 17 Jul 2025 19:13:49 -0300
Rodrigo Gobbi <rodrigo.gobbi.7@...il.com> wrote:

> avg sample info is a bit field coded inside the following
> bits: 5,6,7 and 8 of a device status register.
> 
> channel num info the same, but over bits: 1, 2 and 3.
> 
> mask both values in order to avoid touching other register bits,
> since the first info (avg sample), came from dt.
> 
I read this as meaning this is a hardening change against bad DT rather
than a bug fix?

As such applied for next cycle to the testing branch of iio.git.

Thanks,

Jonathan

> Signed-off-by: Rodrigo Gobbi <rodrigo.gobbi.7@...il.com>
> ---
> About @David comment at v2:
> 
> > For bonus points, a separate patch that cleans up and sorts the existing
> > includes would be appreciated.  
> 
> I`ll change that in a later moment.
> Tks and regards.
> 
> Changelog:
> v3: moving up include; fix indentation;
> v2: https://lore.kernel.org/linux-iio/20250701213728.32064-1-rodrigo.gobbi.7@gmail.com/
> v1: https://lore.kernel.org/linux-iio/20250621185301.9536-1-rodrigo.gobbi.7@gmail.com/#t
> ---
>  drivers/iio/adc/spear_adc.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/adc/spear_adc.c b/drivers/iio/adc/spear_adc.c
> index e3a865c79686..0acc65c74221 100644
> --- a/drivers/iio/adc/spear_adc.c
> +++ b/drivers/iio/adc/spear_adc.c
> @@ -17,6 +17,7 @@
>  #include <linux/clk.h>
>  #include <linux/err.h>
>  #include <linux/completion.h>
> +#include <linux/bitfield.h>
>  
>  #include <linux/iio/iio.h>
>  #include <linux/iio/sysfs.h>
> @@ -29,9 +30,9 @@
>  
>  /* Bit definitions for SPEAR_ADC_STATUS */
>  #define SPEAR_ADC_STATUS_START_CONVERSION	BIT(0)
> -#define SPEAR_ADC_STATUS_CHANNEL_NUM(x)		((x) << 1)
> +#define SPEAR_ADC_STATUS_CHANNEL_NUM_MASK	GENMASK(3, 1)
>  #define SPEAR_ADC_STATUS_ADC_ENABLE		BIT(4)
> -#define SPEAR_ADC_STATUS_AVG_SAMPLE(x)		((x) << 5)
> +#define SPEAR_ADC_STATUS_AVG_SAMPLE_MASK	GENMASK(8, 5)
>  #define SPEAR_ADC_STATUS_VREF_INTERNAL		BIT(9)
>  
>  #define SPEAR_ADC_DATA_MASK		0x03ff
> @@ -157,8 +158,8 @@ static int spear_adc_read_raw(struct iio_dev *indio_dev,
>  	case IIO_CHAN_INFO_RAW:
>  		mutex_lock(&st->lock);
>  
> -		status = SPEAR_ADC_STATUS_CHANNEL_NUM(chan->channel) |
> -			SPEAR_ADC_STATUS_AVG_SAMPLE(st->avg_samples) |
> +		status = FIELD_PREP(SPEAR_ADC_STATUS_CHANNEL_NUM_MASK, chan->channel) |
> +			FIELD_PREP(SPEAR_ADC_STATUS_AVG_SAMPLE_MASK, st->avg_samples) |
>  			SPEAR_ADC_STATUS_START_CONVERSION |
>  			SPEAR_ADC_STATUS_ADC_ENABLE;
>  		if (st->vref_external == 0)