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| author |  Jaewon Kim <jaewon02.kim@samsung.com>
| 2023-05-02 15:28:12 +0900 |
|---|---|---|
| committer |  Mark Brown <broonie@kernel.org>
| 2023-05-08 09:10:51 +0900 |
| commit | 3456674f54d3cfdedb28ce8a3db2b6f975392ac8 (patch) | |
| tree | 0ae125eea2a88810a0bf04e9db18ed5d81aac554 /drivers/spi/spi-s3c64xx.c | |
| parent | spi: s3c64xx: change polling mode to optional (diff) | |
| download | linux-3456674f54d3cfdedb28ce8a3db2b6f975392ac8.tar.gz linux-3456674f54d3cfdedb28ce8a3db2b6f975392ac8.tar.bz2 linux-3456674f54d3cfdedb28ce8a3db2b6f975392ac8.zip | |
spi: s3c64xx: add sleep during transfer
In polling mode, the status register is continuously read to check data
transfer completion. It can cause excessive CPU usage.
To reduce this, we can calculate the transfer time and put the sleep during
transfer.
When test on ExynosAuto9 SADK board, throughput remained the same, but
100% CPU utilization decreased to 40%.
Signed-off-by: Jaewon Kim <jaewon02.kim@samsung.com
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org
Link: https://lore.kernel.org/r/20230502062813.112434-3-jaewon02.kim@samsung.com
Signed-off-by: Mark Brown <broonie@kernel.org
Diffstat (limited to 'drivers/spi/spi-s3c64xx.c')
| -rw-r--r-- | drivers/spi/spi-s3c64xx.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c index 5f59d6f8c8d8..38cc2068afce 100644 --- a/drivers/spi/spi-s3c64xx.c +++ b/drivers/spi/spi-s3c64xx.c @@ -561,11 +561,18 @@ static int s3c64xx_wait_for_pio(struct s3c64xx_spi_driver_data *sdd, u32 cpy_len; u8 *buf; int ms; + unsigned long time_us; - /* millisecs to xfer 'len' bytes @ 'cur_speed' */ - ms = xfer->len * 8 * 1000 / sdd->cur_speed; + /* microsecs to xfer 'len' bytes @ 'cur_speed' */ + time_us = (xfer->len * 8 * 1000 * 1000) / sdd->cur_speed; + ms = (time_us / 1000); ms += 10; /* some tolerance */ + /* sleep during signal transfer time */ + status = readl(regs + S3C64XX_SPI_STATUS); + if (RX_FIFO_LVL(status, sdd) < xfer->len) + usleep_range(time_us / 2, time_us); + val = msecs_to_loops(ms); do { status = readl(regs + S3C64XX_SPI_STATUS); |