linux-kernel - Re: [PATCH v4 3/9] spi: support controllers with multiple data lanes

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Message-ID: <aU_4RhfUlJ5R_inQ@smile.fi.intel.com>
Date: Sat, 27 Dec 2025 17:16:22 +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 v4 3/9] spi: support controllers with multiple data lanes

On Fri, Dec 19, 2025 at 03:32:11PM -0600, David Lechner wrote:
> Add support for SPI controllers with multiple physical SPI data lanes.
> (A data lane in this context means lines connected to a serializer, so a
> controller with two data lanes would have two serializers in a single
> controller).
> 
> This is common in the type of controller that can be used with parallel
> flash memories, but can be used for general purpose SPI as well.
> 
> To indicate support, a controller just needs to set ctlr->num_data_lanes
> to something greater than 1. Peripherals indicate which lane they are
> connected to via device tree (ACPI support can be added if needed).
> 
> The spi-{tx,rx}-bus-width DT properties can now be arrays. The length of
> the array indicates the number of data lanes, and each element indicates
> the bus width of that lane. For now, we restrict all lanes to have the
> same bus width to keep things simple. Support for an optional controller
> lane mapping property is also implemented.

...

> +#define SPI_DEVICE_DATA_LANE_CNT_MAX 8

> +	/* Multi-lane SPI controller support. */
> +	u32			tx_lane_map[SPI_DEVICE_DATA_LANE_CNT_MAX];
> +	u32			num_tx_lanes;
> +	u32			rx_lane_map[SPI_DEVICE_DATA_LANE_CNT_MAX];
> +	u32			num_rx_lanes;

This adds 8*4 + 4 + 8*4 + 4 bytes to the already big enough structure for
the rather rare use cases. Can we start doing it separately and use just
a pointer here?

-- 
With Best Regards,
Andy Shevchenko