| Message ID | 20220525165852.33167-2-eajames@linux.ibm.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 61bf40ef51aa73f6216b33563271b6acf7ea8d70 |
| Headers | show |
| Series | spi: fsi: Fix spurious timeout | expand |
On Wed, May 25, 2022 at 11:58:51AM -0500, Eddie James wrote: > I have one concern still, that if the kernel is very busy, it may > schedule other work for the entire timeout period between assigning > "end" and checking if timed out in the do/while loop... Is it worth > worrying about this case? I'm not sure we can entirely avoid there being a gap, but with it being a busy loop you'd have to be very unlucky to hit that case. If you come up with a fix that'd be nice.
diff --git a/drivers/spi/spi-fsi.c b/drivers/spi/spi-fsi.c index d403a7a3021d..72ab066ce552 100644 --- a/drivers/spi/spi-fsi.c +++ b/drivers/spi/spi-fsi.c @@ -319,12 +319,12 @@ static int fsi_spi_transfer_data(struct fsi_spi *ctx, end = jiffies + msecs_to_jiffies(SPI_FSI_STATUS_TIMEOUT_MS); do { + if (time_after(jiffies, end)) + return -ETIMEDOUT; + rc = fsi_spi_status(ctx, &status, "TX"); if (rc) return rc; - - if (time_after(jiffies, end)) - return -ETIMEDOUT; } while (status & SPI_FSI_STATUS_TDR_FULL); sent += nb; @@ -337,12 +337,12 @@ static int fsi_spi_transfer_data(struct fsi_spi *ctx, while (transfer->len > recv) { end = jiffies + msecs_to_jiffies(SPI_FSI_STATUS_TIMEOUT_MS); do { + if (time_after(jiffies, end)) + return -ETIMEDOUT; + rc = fsi_spi_status(ctx, &status, "RX"); if (rc) return rc; - - if (time_after(jiffies, end)) - return -ETIMEDOUT; } while (!(status & SPI_FSI_STATUS_RDR_FULL)); rc = fsi_spi_read_reg(ctx, SPI_FSI_DATA_RX, &in);
The driver may return a timeout error even if the status register indicates that the transfer may proceed. Fix this by restructuring the polling loop. Fixes: 89b35e3f2851 ("spi: fsi: Implement a timeout for polling status") Signed-off-by: Eddie James <eajames@linux.ibm.com> --- I have one concern still, that if the kernel is very busy, it may schedule other work for the entire timeout period between assigning "end" and checking if timed out in the do/while loop... Is it worth worrying about this case? drivers/spi/spi-fsi.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)