linux-kernel - Re: [PATCH] iio: humidity: hdc100x: Add margin to the conversion time

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Message-ID: <20210610104136.00002e4e@Huawei.com>
Date:   Thu, 10 Jun 2021 10:41:36 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Chris Lesiak <chris.lesiak@...or.com>
CC:     Jonathan Cameron <jic23@...nel.org>, <linux-iio@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iio: humidity: hdc100x: Add margin to the conversion
 time

On Wed,  9 Jun 2021 14:37:48 -0500
Chris Lesiak <chris.lesiak@...or.com> wrote:

> The datasheets have the following note for the conversion time
> specification: "This parameter is specified by design and/or
> characterization and it is not tested in production."
> 
> Parts have been seen that require more time to do 14-bit conversions for
> the relative humidity channel.  The result is ENXIO due to the address
> phase of a transfer not getting an ACK.
> 
> Delay an additional 1 ms per conversion to allow for additional margin.
> 
> Signed-off-by: Chris Lesiak <chris.lesiak@...or.com>

Hi Chris

Could you figure out a fixes tag for this one so we can get it backported
into stable?

If not I can probably guess when I catch up with applying patches.

Thanks,

Jonathan

> ---
>  drivers/iio/humidity/hdc100x.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/humidity/hdc100x.c b/drivers/iio/humidity/hdc100x.c
> index 2a957f19048e..91790aa8beeb 100644
> --- a/drivers/iio/humidity/hdc100x.c
> +++ b/drivers/iio/humidity/hdc100x.c
> @@ -166,7 +166,7 @@ static int hdc100x_get_measurement(struct hdc100x_data *data,
>  				   struct iio_chan_spec const *chan)
>  {
>  	struct i2c_client *client = data->client;
> -	int delay = data->adc_int_us[chan->address];
> +	int delay = data->adc_int_us[chan->address] + 1000;
>  	int ret;
>  	__be16 val;
>  
> @@ -316,7 +316,7 @@ static irqreturn_t hdc100x_trigger_handler(int irq, void *p)
>  	struct iio_dev *indio_dev = pf->indio_dev;
>  	struct hdc100x_data *data = iio_priv(indio_dev);
>  	struct i2c_client *client = data->client;
> -	int delay = data->adc_int_us[0] + data->adc_int_us[1];
> +	int delay = data->adc_int_us[0] + data->adc_int_us[1] + 2000;
>  	int ret;
>  
>  	/* dual read starts at temp register */