5.4-stable review patch. If anyone has any objections, please let me know.
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From: Stefan Wahren wahrenst@gmx.net
[ Upstream commit 730bbfaf7d4890bd99e637db7767dc68cfeb24e7 ]
The effective SPI clock frequency should never exceed speed_hz otherwise this might result in undefined behavior of the SPI device.
Currently the scldiv calculation could violate this constraint. For the example parameters perclk_rate = 24 MHz and speed_hz = 7 MHz, the function fsl_lpspi_set_bitrate will determine perscale = 0 and scldiv = 1, which is a effective SPI clock of 8 MHz.
So fix this by rounding up the quotient of perclk_rate and speed_hz. While this never change within the loop, we can pull this out.
Fixes: 5314987de5e5 ("spi: imx: add lpspi bus driver") Signed-off-by: Stefan Wahren wahrenst@gmx.net Link: https://patch.msgid.link/20240804113611.83613-1-wahrenst@gmx.net Signed-off-by: Mark Brown broonie@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/spi/spi-fsl-lpspi.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c index 5351185fd9af7..2708bf15e1263 100644 --- a/drivers/spi/spi-fsl-lpspi.c +++ b/drivers/spi/spi-fsl-lpspi.c @@ -317,7 +317,7 @@ static void fsl_lpspi_set_watermark(struct fsl_lpspi_data *fsl_lpspi) static int fsl_lpspi_set_bitrate(struct fsl_lpspi_data *fsl_lpspi) { struct lpspi_config config = fsl_lpspi->config; - unsigned int perclk_rate, scldiv; + unsigned int perclk_rate, scldiv, div; u8 prescale;
perclk_rate = clk_get_rate(fsl_lpspi->clk_per); @@ -328,8 +328,10 @@ static int fsl_lpspi_set_bitrate(struct fsl_lpspi_data *fsl_lpspi) return -EINVAL; }
+ div = DIV_ROUND_UP(perclk_rate, config.speed_hz); + for (prescale = 0; prescale < 8; prescale++) { - scldiv = perclk_rate / config.speed_hz / (1 << prescale) - 2; + scldiv = div / (1 << prescale) - 2; if (scldiv < 256) { fsl_lpspi->config.prescale = prescale; break;