Unverified Commit d8e4ebf8 authored Jun 22, 2023 by Miquel Raynal Committed by Mark Brown Jun 22, 2023

spi: Create a helper to derive adaptive timeouts



Big transfers might take a bit of time, too constraining timeouts might
lead to false positives. In order to simplify the drivers work and with
the goal of factorizing code in mind, let's add a helper that can be
used by any spi controller driver to derive a relevant per-transfer
timeout value.

The logic is simple: we know how much time it would take to transfer a
byte, we can easily derive the total theoretical amount of time involved
for each transfer. We multiply it by two to have a bit of margin and
enforce a minimum of 500ms.

Suggested-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/Message-Id

: <20230622090634.3411468-2-miquel.raynal@bootlin.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

parent e6afe033

include/linux/spi/spi.h

+17 −0

Original line number	Diff line number	Diff line
		@@ -1261,6 +1261,23 @@ static inline bool spi_is_bpw_supported(struct spi_device *spi, u32 bpw)
		return false;
		}

		/**
		* spi_controller_xfer_timeout - Compute a suitable timeout value
		* @ctlr: SPI device
		* @xfer: Transfer descriptor
		*
		* Compute a relevant timeout value for the given transfer. We derive the time
		* that it would take on a single data line and take twice this amount of time
		* with a minimum of 500ms to avoid false positives on loaded systems.
		*
		* Returns: Transfer timeout value in milliseconds.
		*/
		static inline unsigned int spi_controller_xfer_timeout(struct spi_controller *ctlr,
		struct spi_transfer *xfer)
		{
		return max(xfer->len * 8 * 2 / (xfer->speed_hz / 1000), 500U);
		}

		/---------------------------------------------------------------------------/

		/* SPI transfer replacement methods which make use of spi_res */