| Message ID | 20200905151913.117775-1-marex@denx.de (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | ea8be08cc9358f811e4175ba7fa7fea23c5d393e |
| Headers | show |
| Series | spi: stm32: Rate-limit the 'Communication suspended' message | expand |
On Sat, 5 Sep 2020 17:19:13 +0200, Marek Vasut wrote: > The 'spi_stm32 44004000.spi: Communication suspended' message means that > when using PIO, the kernel did not read the FIFO fast enough and so the > SPI controller paused the transfer. Currently, this is printed on every > single such event, so if the kernel is busy and the controller is pausing > the transfers often, the kernel will be all the more busy scrolling this > message into the log buffer every few milliseconds. That is not helpful. > > [...] Applied to https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next Thanks! [1/1] spi: stm32: Rate-limit the 'Communication suspended' message commit: ea8be08cc9358f811e4175ba7fa7fea23c5d393e All being well this means that it will be integrated into the linux-next tree (usually sometime in the next 24 hours) and sent to Linus during the next merge window (or sooner if it is a bug fix), however if problems are discovered then the patch may be dropped or reverted. You may get further e-mails resulting from automated or manual testing and review of the tree, please engage with people reporting problems and send followup patches addressing any issues that are reported if needed. If any updates are required or you are submitting further changes they should be sent as incremental updates against current git, existing patches will not be replaced. Please add any relevant lists and maintainers to the CCs when replying to this mail. Thanks, Mark
diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c index d4b33b358a31..a00f6b51ccbf 100644 --- a/drivers/spi/spi-stm32.c +++ b/drivers/spi/spi-stm32.c @@ -936,7 +936,11 @@ static irqreturn_t stm32h7_spi_irq_thread(int irq, void *dev_id) } if (sr & STM32H7_SPI_SR_SUSP) { - dev_warn(spi->dev, "Communication suspended\n"); + static DEFINE_RATELIMIT_STATE(rs, + DEFAULT_RATELIMIT_INTERVAL * 10, + 1); + if (__ratelimit(&rs)) + dev_dbg_ratelimited(spi->dev, "Communication suspended\n"); if (!spi->cur_usedma && (spi->rx_buf && (spi->rx_len > 0))) stm32h7_spi_read_rxfifo(spi, false); /*
The 'spi_stm32 44004000.spi: Communication suspended' message means that when using PIO, the kernel did not read the FIFO fast enough and so the SPI controller paused the transfer. Currently, this is printed on every single such event, so if the kernel is busy and the controller is pausing the transfers often, the kernel will be all the more busy scrolling this message into the log buffer every few milliseconds. That is not helpful. Instead, rate-limit the message and print it every once in a while. It is not possible to use the default dev_warn_ratelimited(), because that is still too verbose, as it prints 10 lines (DEFAULT_RATELIMIT_BURST) every 5 seconds (DEFAULT_RATELIMIT_INTERVAL). The policy here is to print 1 line every 50 seconds (DEFAULT_RATELIMIT_INTERVAL * 10), because 1 line is more than enough and the cycles saved on printing are better left to the CPU to handle the SPI. However, dev_warn_once() is also not useful, as the user should be aware that this condition is possibly recurring or ongoing. Thus the custom rate-limit policy. Finally, turn the message from dev_warn() to dev_dbg(), since the system does not suffer any sort of malfunction if this message appears, it is just slowing down. This further reduces the printing into the log buffer and frees the CPU to do useful work. Fixes: dcbe0d84dfa5 ("spi: add driver for STM32 SPI controller") Signed-off-by: Marek Vasut <marex@denx.de> Cc: Alexandre Torgue <alexandre.torgue@st.com> Cc: Amelie Delaunay <amelie.delaunay@st.com> Cc: Antonio Borneo <borneo.antonio@gmail.com> Cc: Mark Brown <broonie@kernel.org> --- drivers/spi/spi-stm32.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)