linux-kernel - Re: [PATCH 3/4] iio: adc: ad4000: Use device specific timing for SPI transfers

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Message-ID: <7e302a49-db5a-444d-aae1-3c80ab75b471@baylibre.com>
Date: Fri, 15 Nov 2024 11:07:34 -0600
From: David Lechner <dlechner@...libre.com>
To: Marcelo Schmitt <marcelo.schmitt@...log.com>, lars@...afoo.de,
 Michael.Hennerich@...log.com, jic23@...nel.org, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, marcelo.schmitt1@...il.com
Cc: linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] iio: adc: ad4000: Use device specific timing for SPI
 transfers

On 11/14/24 5:51 PM, Marcelo Schmitt wrote:
> The SPI transfers for AD4020, AD4021, and AD4022 have slightly different
> timing specifications. Use device specific timing constraints to set SPI
> transfer parameters.
> 
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
> ---
>  drivers/iio/adc/ad4000.c | 50 ++++++++++++++++++++++++++++++++--------
>  1 file changed, 41 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad4000.c b/drivers/iio/adc/ad4000.c
> index 21731c4d31ee..68ac77494263 100644
> --- a/drivers/iio/adc/ad4000.c
> +++ b/drivers/iio/adc/ad4000.c
> @@ -35,10 +35,6 @@
>  
>  #define AD4000_SCALE_OPTIONS		2
>  
> -#define AD4000_TQUIET1_NS		190
> -#define AD4000_TQUIET2_NS		60
> -#define AD4000_TCONV_NS			320

We are removing 3 but only adding 2 in the struct below?

If one of these was unused, best to mention it in the commit message.

> -
>  #define __AD4000_DIFF_CHANNEL(_sign, _real_bits, _storage_bits, _reg_access)	\
>  {										\
>  	.type = IIO_VOLTAGE,							\
> @@ -122,10 +118,30 @@ static const int ad4000_gains[] = {
>  	454, 909, 1000, 1900,
>  };
>  
> +struct ad4000_time_spec {
> +	int t_conv_ns;
> +	int t_quiet2_ns;
> +};
> +
> +/*
> + * Same timing specifications for all of AD4000, AD4001, ..., AD4008, AD4010,
> + * ADAQ4001, and ADAQ4003.
> + */
> +static const struct ad4000_time_spec ad4000_t_spec = {
> +	.t_conv_ns = 320,
> +	.t_quiet2_ns = 60,
> +};
> +
> +static const struct ad4000_time_spec ad4020_t_spec = {
> +	.t_conv_ns = 350,
> +	.t_quiet2_ns = 60,
> +};

t_quiet2_ns is the same in both cases, so do we actually need to
add it here instead of using a common macro? Or if it is for future
differences, mention that in the commit message.