From ea8be08cc9358f811e4175ba7fa7fea23c5d393e Mon Sep 17 00:00:00 2001 From: Marek Vasut Date: Sat, 5 Sep 2020 17:19:13 +0200 Subject: [PATCH] spi: stm32: Rate-limit the 'Communication suspended' message 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 Cc: Alexandre Torgue Cc: Amelie Delaunay Cc: Antonio Borneo Cc: Mark Brown Link: https://lore.kernel.org/r/20200905151913.117775-1-marex@denx.de Signed-off-by: Mark Brown --- drivers/spi/spi-stm32.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) 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); /* -- 2.34.1