linux-kernel - Re: [PATCH v3 6/9] iio: dac: ad3552r-hs: use instruction mode for configuration

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Message-ID: <bacd718d-4e6c-48d7-860f-e6de26bed416@baylibre.com>
Date: Fri, 10 Jan 2025 09:37:20 -0600
From: David Lechner <dlechner@...libre.com>
To: Angelo Dureghello <adureghello@...libre.com>,
 Lars-Peter Clausen <lars@...afoo.de>,
 Michael Hennerich <Michael.Hennerich@...log.com>,
 Jonathan Cameron <jic23@...nel.org>, Nuno Sa <nuno.sa@...log.com>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 6/9] iio: dac: ad3552r-hs: use instruction mode for
 configuration

On 1/10/25 4:24 AM, Angelo Dureghello wrote:
> From: Angelo Dureghello <adureghello@...libre.com>
> 
> Use "instruction" mode over initial configuration and all other
> non-streaming operations.
> 
> DAC boots in streaming mode as default, and the driver is not
> changing this mode.
> 
> Instruction r/w is still working becouse instruction is processed

s/becouse/because/

> from the DAC after chip select is deasserted, this works until
> loop mode is 0 or greater than the instruction size.
> 
> All initial operations should be more safely done in instruction
> mode, a mode provided for this.
> 
> Signed-off-by: Angelo Dureghello <adureghello@...libre.com>
> ---
>  drivers/iio/dac/ad3552r-hs.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/drivers/iio/dac/ad3552r-hs.c b/drivers/iio/dac/ad3552r-hs.c
> index 27949f207d42..991b11702273 100644
> --- a/drivers/iio/dac/ad3552r-hs.c
> +++ b/drivers/iio/dac/ad3552r-hs.c
> @@ -132,6 +132,13 @@ static int ad3552r_hs_buffer_postenable(struct iio_dev *indio_dev)
>  		return -EINVAL;
>  	}
>  
> +	/* Primary region access, set streaming mode (now in SPI + SDR). */
> +	ret = ad3552r_qspi_update_reg_bits(st,
> +					   AD3552R_REG_ADDR_INTERFACE_CONFIG_B,
> +					   AD3552R_MASK_SINGLE_INST, 0, 1);
> +	if (ret)
> +		return ret;

Do we need to undo this operation before we return in the case of an error
later in this function?

> +
>  	ret = st->data->bus_reg_write(st->back, AD3552R_REG_ADDR_STREAM_MODE,
>  				      loop_len, 1);
>  	if (ret)