Re: [PATCH 3/3] spi: dw: Use the rx-sample-delay-ns value parsed by the core

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] spi: dw: unable to override controller rx-sample-delay-ns to 0
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commit 32c003f916e2933421d0880f812a21d5785775b7
Author: Frieder Schrempf <frieder.schrempf@kontron.de>

spi: dw: Use the rx-sample-delay-ns value parsed by the core

This commit drops the private parsing of the rx-sample-delay-ns property
and uses the value parsed by the core into spi_device.rx_sample_delay_ns.
It falls back to the controller-wide default when the device does not ask
for a delay of its own.

> diff --git a/drivers/spi/spi-dw-core.c b/drivers/spi/spi-dw-core.c
> index 206d3f9dd83d4..b86b607cc8179 100644
> --- a/drivers/spi/spi-dw-core.c
> +++ b/drivers/spi/spi-dw-core.c
> @@ -1104,12 +1104,13 @@ static int dw_spi_setup(struct spi_device *spi)
[ ... ]
> -		/* Get specific / default rx-sample-delay */
> -		if (device_property_read_u32(&spi->dev,
> -					     "rx-sample-delay-ns",
> -					     &rx_sample_dly_ns) != 0)
> -			/* Use default controller value */
> -			rx_sample_dly_ns = dws->def_rx_sample_dly_ns;
> +		/*
> +		 * Use the per-device value the core parsed from the peripheral
> +		 * node, and fall back to the controller-wide default when the
> +		 * device does not ask for a delay of its own.
> +		 */
> +		rx_sample_dly_ns = spi->rx_sample_delay_ns ?:
> +				   dws->def_rx_sample_dly_ns;

[Severity: Medium]
Does this ?: operator prevent configuring an explicit 0 ns delay?

The previous code used device_property_read_u32() in dw_spi_setup(),
which allowed an explicit value of 0 to override the controller default:

    if (device_property_read_u32(...) != 0)
        rx_sample_dly_ns = dws->def_rx_sample_dly_ns;

By using the ?: operator, a parsed value of 0 is treated as falsy,
meaning an explicit rx-sample-delay-ns = <0> in the device tree will
now fall back to the controller's default instead of overriding it to 0.

Although the commit message states there are no in-tree users relying
on this behavior, Device Tree is a stable ABI. Does ignoring the explicit
override of <0> break backward compatibility for out-of-tree configurations,
potentially causing SPI RX data corruption on boards that require a 0 ns
delay?

>  		chip->rx_sample_dly = DIV_ROUND_CLOSEST(rx_sample_dly_ns,
>  							NSEC_PER_SEC /
>  							dws->max_freq);

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Sashiko AI review · https://sashiko.dev/#/patchset/20260917-spi-sample-delay-cleanup-v1-0-0e4eddbfb1ce@kontron.de?part=3