On 19/04/2023 08:06, Jaewon Kim wrote:
> In polling mode, the status register is constantly read to check transfer
> completion. It cause excessive CPU usage.
> So, it calculates the SPI transfer time and made it sleep.
>
> Signed-off-by: Jaewon Kim <jaewon02.kim@xxxxxxxxxxx>
> ---
> drivers/spi/spi-s3c64xx.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
> index 886722fb40ea..cf3060b2639b 100644
> --- a/drivers/spi/spi-s3c64xx.c
> +++ b/drivers/spi/spi-s3c64xx.c
> @@ -561,6 +561,14 @@ static int s3c64xx_wait_for_pio(struct s3c64xx_spi_driver_data *sdd,
> u32 cpy_len;
> u8 *buf;
> int ms;
> + u32 tx_time;
> +
> + /* sleep during signal transfer time */
> + status = readl(regs + S3C64XX_SPI_STATUS);
> + if (RX_FIFO_LVL(status, sdd) < xfer->len) {
> + tx_time = (xfer->len * 8 * 1000 * 1000) / sdd->cur_speed;
> + usleep_range(tx_time / 2, tx_time);
> + }
Did you actually check the delays introduced by it? Is it worth?
>
> /* millisecs to xfer 'len' bytes @ 'cur_speed' */
> ms = xfer->len * 8 * 1000 / sdd->cur_speed;
You have now some code duplication so this could be combined.
Best regards,
Krzysztof
