Unverified Commit a77541ca authored by Mark Brown's avatar Mark Brown
Browse files

spi: Helper for deriving timeout values 

Merge series from Miquel Raynal <miquel.raynal@bootlin.com>:

I recently came across an issue with the Atmel spi controller driver
which would stop my transfers after a too small timeout when performing
big transfers (reading a 4MiB flash in one transfer). My initial idea
was to derive a the maximum amount of time a transfer would take
depending on its size and use that as value to avoid erroring-out when
not relevant. Mark wanted to go further by creating a core helper doing
that, based on the heuristics from the sun6i driver.

Here is a small series of 3 patches doing exactly that.
parents 01fa9edd 6eef8955

drivers/spi/spi-atmel.c

+11 −7
Original line number Diff line number Diff line
@@ -233,7 +233,8 @@ 
 */

#define DMA_MIN_BYTES	16



#define SPI_DMA_TIMEOUT		(msecs_to_jiffies(1000))

#define SPI_DMA_MIN_TIMEOUT	(msecs_to_jiffies(1000))

#define SPI_DMA_TIMEOUT_PER_10K	(msecs_to_jiffies(4))



#define AUTOSUSPEND_TIMEOUT	2000
@@ -1279,7 +1280,8 @@ static int atmel_spi_one_transfer(struct spi_controller *host, 
	struct atmel_spi_device	*asd;

	int			timeout;

	int			ret;

	unsigned long		dma_timeout;

	unsigned int		dma_timeout;

	long			ret_timeout;



	as = spi_controller_get_devdata(host);
@@ -1333,11 +1335,13 @@ static int atmel_spi_one_transfer(struct spi_controller *host, 
			atmel_spi_unlock(as);

		}



		dma_timeout = wait_for_completion_timeout(&as->xfer_completion,

							  SPI_DMA_TIMEOUT);

		if (WARN_ON(dma_timeout == 0)) {

			dev_err(&spi->dev, "spi transfer timeout\n");

			as->done_status = -EIO;

		dma_timeout = msecs_to_jiffies(spi_controller_xfer_timeout(host, xfer));

		ret_timeout = wait_for_completion_interruptible_timeout(&as->xfer_completion,

									dma_timeout);

		if (ret_timeout <= 0) {

			dev_err(&spi->dev, "spi transfer %s\n",

				!ret_timeout ? "timeout" : "canceled");

			as->done_status = ret_timeout < 0 ? ret_timeout : -EIO;

		}



		if (as->done_status)

drivers/spi/spi-sun6i.c

+1 −1
Original line number Diff line number Diff line
@@ -455,7 +455,7 @@ static int sun6i_spi_transfer_one(struct spi_master *master, 
	reg = sun6i_spi_read(sspi, SUN6I_TFR_CTL_REG);

	sun6i_spi_write(sspi, SUN6I_TFR_CTL_REG, reg | SUN6I_TFR_CTL_XCH);



	tx_time = max(tfr->len * 8 * 2 / (tfr->speed_hz / 1000), 100U);

	tx_time = spi_controller_xfer_timeout(master, tfr);

	start = jiffies;

	timeout = wait_for_completion_timeout(&sspi->done,

					      msecs_to_jiffies(tx_time));

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 */