[PATCH] iio: adc: ad7793: replace usleep_range() with fsleep()

[PATCH] iio: adc: ad7793: replace usleep_range() with fsleep()

[Stepan Ionichev]

The AD7792/AD7793 datasheet (Rev. B, page 25, RESET section)
says: "When a reset is initiated, the user must allow a period
of 500 us before accessing any of the on-chip registers."

Use fsleep(500) instead of usleep_range(500, 2000). The 500 us
minimum stays the same; fsleep() picks the upper slack itself
(about +25% on a default config -- narrower than the original
2000 us).

Add a code comment with the datasheet reference so the "why"
of the wait is visible at the call site.

Signed-off-by: Stepan Ionichev <sozdayvek@gmail.com>
---
 drivers/iio/adc/ad7793.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/ad7793.c b/drivers/iio/adc/ad7793.c
index 8ff7b70d6..dbc6b47b7 100644
--- a/drivers/iio/adc/ad7793.c
+++ b/drivers/iio/adc/ad7793.c
@@ -268,7 +268,12 @@ static int ad7793_setup(struct iio_dev *indio_dev,
 	ret = ad_sd_reset(&st->sd);
 	if (ret < 0)
 		goto out;
-	usleep_range(500, 2000); /* Wait for at least 500us */
+
+	/*
+	 * Per AD7792/AD7793 datasheet (Rev. B, page 25, RESET section),
+	 * allow 500 us after a reset before accessing on-chip registers.
+	 */
+	fsleep(500);
 
 	/* write/read test for device presence */
 	ret = ad_sd_read_reg(&st->sd, AD7793_REG_ID, 1, &id);
-- 
2.43.0

Re: [PATCH] iio: adc: ad7793: replace usleep_range() with fsleep()

[Andy Shevchenko]

On Mon, May 11, 2026 at 10:30:43AM +0500, Stepan Ionichev wrote:
> The AD7792/AD7793 datasheet (Rev. B, page 25, RESET section)
> says: "When a reset is initiated, the user must allow a period
> of 500 us before accessing any of the on-chip registers."
> 
> Use fsleep(500) instead of usleep_range(500, 2000). The 500 us
> minimum stays the same; fsleep() picks the upper slack itself
> (about +25% on a default config -- narrower than the original
> 2000 us).

> Add a code comment with the datasheet reference so the "why"
> of the wait is visible at the call site.

Unneeded detail in the commit message (it more appropriate
to have this in the comment block, below '---' line). Up to
Jonathan what to do with it.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] iio: adc: ad7793: replace usleep_range() with fsleep()

[Jonathan Cameron]

On Mon, 11 May 2026 10:30:43 +0500
Stepan Ionichev <sozdayvek@gmail.com> wrote:

> The AD7792/AD7793 datasheet (Rev. B, page 25, RESET section)
> says: "When a reset is initiated, the user must allow a period
> of 500 us before accessing any of the on-chip registers."
> 
> Use fsleep(500) instead of usleep_range(500, 2000). The 500 us
> minimum stays the same; fsleep() picks the upper slack itself
> (about +25% on a default config -- narrower than the original
> 2000 us).
> 
> Add a code comment with the datasheet reference so the "why"
> of the wait is visible at the call site.
> 
> Signed-off-by: Stepan Ionichev <sozdayvek@gmail.com>
Nice

Applied to the testing branch of iio.git.

Thanks,

Jonathan

> ---
>  drivers/iio/adc/ad7793.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/adc/ad7793.c b/drivers/iio/adc/ad7793.c
> index 8ff7b70d6..dbc6b47b7 100644
> --- a/drivers/iio/adc/ad7793.c
> +++ b/drivers/iio/adc/ad7793.c
> @@ -268,7 +268,12 @@ static int ad7793_setup(struct iio_dev *indio_dev,
>  	ret = ad_sd_reset(&st->sd);
>  	if (ret < 0)
>  		goto out;
> -	usleep_range(500, 2000); /* Wait for at least 500us */
> +
> +	/*
> +	 * Per AD7792/AD7793 datasheet (Rev. B, page 25, RESET section),
> +	 * allow 500 us after a reset before accessing on-chip registers.
> +	 */
> +	fsleep(500);
>  
>  	/* write/read test for device presence */
>  	ret = ad_sd_read_reg(&st->sd, AD7793_REG_ID, 1, &id);

Re: [PATCH] iio: adc: ad7793: replace usleep_range() with fsleep()

[Jonathan Cameron]

On Mon, 11 May 2026 16:21:39 +0300
Andy Shevchenko <andriy.shevchenko@intel.com> wrote:

> On Mon, May 11, 2026 at 10:30:43AM +0500, Stepan Ionichev wrote:
> > The AD7792/AD7793 datasheet (Rev. B, page 25, RESET section)
> > says: "When a reset is initiated, the user must allow a period
> > of 500 us before accessing any of the on-chip registers."
> > 
> > Use fsleep(500) instead of usleep_range(500, 2000). The 500 us
> > minimum stays the same; fsleep() picks the upper slack itself
> > (about +25% on a default config -- narrower than the original
> > 2000 us).  
> 
> > Add a code comment with the datasheet reference so the "why"
> > of the wait is visible at the call site.  
> 
> Unneeded detail in the commit message (it more appropriate
> to have this in the comment block, below '---' line). Up to
> Jonathan what to do with it.
> 
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
> 
I left the comment on the comment.  Not needed perhaps but not
harmful either.