| Message ID | 20230622090634.3411468-3-miquel.raynal@bootlin.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | spi: Helper for deriving timeout values | expand |
On 6/22/23 02:06, Miquel Raynal wrote: > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe > > 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 <miquel.raynal@bootlin.com> Acked-by: Ryan Wanner <ryan.wanner@microchip.com> > --- > 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 943548aab8af..d87be2890597 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) > -- > 2.34.1 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c index 943548aab8af..d87be2890597 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)
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 <miquel.raynal@bootlin.com> --- drivers/spi/spi-atmel.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-)