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

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[ 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: 77736a98b8 ("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>
This commit is contained in:
Stefan Wahren 2025-08-07 12:07:42 +02:00 committed by Greg Kroah-Hartman
parent a9e5924daa
commit aa2b0dc332
1 changed files with 3 additions and 5 deletions
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8
drivers/spi/spi-fsl-lpspi.c
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@ -330,13 +330,11 @@ 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) {