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.

2 files changed, 12 insertions, 8 deletions

diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
index 7f06305e16cb..152cd6773403 100644
--- a/drivers/spi/spi-atmel.c
+++ b/drivers/spi/spi-atmel.c
@@ -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)
diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
index 02a3a4f2b3a0..30d541612253 100644
--- a/drivers/spi/spi-sun6i.c
+++ b/drivers/spi/spi-sun6i.c
@@ -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));