From d8e4ebf87018736c0c29e2eb4afe3915156483cd Mon Sep 17 00:00:00 2001 From: Miquel Raynal Date: Thu, 22 Jun 2023 11:06:32 +0200 Subject: 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 Signed-off-by: Miquel Raynal Link: https://lore.kernel.org/r/Message-Id: <20230622090634.3411468-2-miquel.raynal@bootlin.com> Signed-off-by: Mark Brown --- include/linux/spi/spi.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index cfe42f8cd7a4..32c94eae8926 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -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 */ -- cgit v1.2.3 From e0205d6203c2ce598ae26d4b2707ca4224a9c90b Mon Sep 17 00:00:00 2001 From: Miquel Raynal Date: Thu, 22 Jun 2023 11:06:33 +0200 Subject: spi: atmel: Prevent false timeouts on long transfers A slow SPI bus clocks at ~20MHz, which means it would transfer about 2500 bytes per second with a single data line. Big transfers, like when dealing with flashes can easily reach a few MiB. The current DMA timeout is set to 1 second, which means any working transfer of about 4MiB will always be cancelled. With the above derivations, on a slow bus, we can assume every byte will take at most 0.4ms. Said otherwise, we could add 4ms to the 1-second timeout delay every 10kiB. On a 4MiB transfer, it would bring the timeout delay up to 2.6s which still seems rather acceptable for a timeout. The consequence of this is that long transfers might be allowed, which hence requires the need to interrupt the transfer if wanted by the user. We can hence switch to the _interruptible variant of wait_for_completion. This leads to a little bit more handling to also handle the interrupted case but looks really acceptable overall. While at it, we drop the useless, noisy and redundant WARN_ON() call. Signed-off-by: Miquel Raynal Acked-by: Ryan Wanner Link: https://lore.kernel.org/r/Message-Id: <20230622090634.3411468-3-miquel.raynal@bootlin.com> Signed-off-by: Mark Brown --- drivers/spi/spi-atmel.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 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) -- cgit v1.2.3 From 6eef895581c9b5fcd002ff77837e0c3a4b1eecf6 Mon Sep 17 00:00:00 2001 From: Miquel Raynal Date: Thu, 22 Jun 2023 11:06:34 +0200 Subject: spi: sun6i: Use the new helper to derive the xfer timeout value MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit A helper was recently added to the core to factorize common code between drivers, like the amount of time a driver should wait for a transfer to happen. It is of course possible to use a default value (like eg. 1s) but it is way stronger to adapt this amount of time to the transfer. Indeed, long transfers (eg. 4MiB) on a slow single-spi bus might take more than the usual second of timeout and prevent lengthy transfers. The core helper was heavily inspired by the logic applied in this driver, the only difference being the minimum amount of time which was enlarged from 0.1s to 0.5s. Use this helper instead of open-coding it. Signed-off-by: Miquel Raynal Acked-by: Jernej Škrabec Link: https://lore.kernel.org/r/Message-Id: <20230622090634.3411468-4-miquel.raynal@bootlin.com> Signed-off-by: Mark Brown --- drivers/spi/spi-sun6i.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) 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)); -- cgit v1.2.3