linux-kernel - Re: [PATCH v3 4/7] spi: axi-spi-engine: support SPI_MULTI_LANE_MODE

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Message-ID: <aS79ex5Konr_EeMA@smile.fi.intel.com>
Date: Tue, 2 Dec 2025 16:53:47 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: David Lechner <dlechner@...libre.com>
Cc: Mark Brown <broonie@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Marcelo Schmitt <marcelo.schmitt@...log.com>,
	Michael Hennerich <michael.hennerich@...log.com>,
	Nuno Sá <nuno.sa@...log.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Andy Shevchenko <andy@...nel.org>,
	Sean Anderson <sean.anderson@...ux.dev>, linux-spi@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-iio@...r.kernel.org
Subject: Re: [PATCH v3 4/7] spi: axi-spi-engine: support
 SPI_MULTI_LANE_MODE_STRIPE

On Mon, Dec 01, 2025 at 08:20:42PM -0600, David Lechner wrote:
> Add support for SPI_MULTI_LANE_MODE_STRIPE to the AXI SPI engine driver.
> 
> The v2.0.0 version of the AXI SPI Engine IP core supports multiple
> lanes. This can be used with SPI_MULTI_LANE_MODE_STRIPE to support
> reading from simultaneous sampling ADCs that have a separate SDO line
> for each analog channel. This allows reading all channels at the same
> time to increase throughput.

...

> +static u8 spi_engine_all_lane_flags(struct spi_device *spi)
> +{
> +	u8 flags = 0;

> +	int i;

Why signed?

> +	for (i = 0; i < spi->num_data_lanes; i++)
> +		flags |= BIT(spi->data_lanes[i]);
> +
> +	return flags;
> +}

...

>  static void spi_engine_gen_xfer(struct spi_engine_program *p, bool dry,
> -	struct spi_transfer *xfer)
> +				struct spi_transfer *xfer, u32 num_lanes)

Side note: this bool parameter makes code harder to follow. And now we have
pointers and integers/booleans to be interleaved. Perhaps reconsider the order
of the parameters (and ideally get rid of boolean by making two distinct
functions?).

...

>  	version = readl(spi_engine->base + ADI_AXI_REG_VERSION);
> -	if (ADI_AXI_PCORE_VER_MAJOR(version) != 1) {
> +	if (ADI_AXI_PCORE_VER_MAJOR(version) > 2) {

But this includes v0 as well!

>  	}

-- 
With Best Regards,
Andy Shevchenko