spi: spi-fsl-lpspi: Clamp too high speed_hz

[ Upstream commit af357a6a3b7d685e7aa621c6fb1d4ed6c349ec9e ]

Currently the driver is not able to handle the case that a SPI device
specifies a higher spi-max-frequency than half of per-clk:

    per-clk should be at least two times of transfer speed

Fix this by clamping to the max possible value and use the minimum SCK
period of 2 cycles.

Fixes: 77736a98b859 ("spi: lpspi: add the error info of transfer speed setting")
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Link: https://patch.msgid.link/20250807100742.9917-1-wahrenst@gmx.net
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c
index 5e381844523440c03b1d0bbe4a044f28fbfbc738..1a22d356a73d950d27ec76baa0670b052c3b6e19 100644 (file)
--- a/drivers/spi/spi-fsl-lpspi.c
+++ b/drivers/spi/spi-fsl-lpspi.c
@@ -331,13 +331,11 @@ static int fsl_lpspi_set_bitrate(struct fsl_lpspi_data *fsl_lpspi)
        }
 
        if (config.speed_hz > perclk_rate / 2) {
-               dev_err(fsl_lpspi->dev,
-                     "per-clk should be at least two times of transfer speed");
-               return -EINVAL;
+               div = 2;
+       } else {
+               div = DIV_ROUND_UP(perclk_rate, config.speed_hz);
        }
 
-       div = DIV_ROUND_UP(perclk_rate, config.speed_hz);
-
        for (prescale = 0; prescale <= prescale_max; prescale++) {
                scldiv = div / (1 << prescale) - 2;
                if (scldiv >= 0 && scldiv < 256) {