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| author | Stefan Wahren <wahrenst@gmx.net> | 2024-08-04 14:36:11 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-08-14 14:58:52 +0300 |
| commit | a2c0f5df8b6b0c5828607f4b767812e0ba83f5c3 (patch) | |
| tree | 4a997f4c1a8df8ea3a2e5e01d276a348d6affcb1 | |
| parent | c25b8a3f016a8ab1423b381fe51f706dd8557fbb (diff) | |
| download | linux-a2c0f5df8b6b0c5828607f4b767812e0ba83f5c3.tar.xz | |
spi: spi-fsl-lpspi: Fix scldiv calculation
[ 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>
| -rw-r--r-- | drivers/spi/spi-fsl-lpspi.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c index 079035db7dd8..3c0f7dc9614d 100644 --- a/drivers/spi/spi-fsl-lpspi.c +++ b/drivers/spi/spi-fsl-lpspi.c @@ -296,7 +296,7 @@ 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); @@ -313,8 +313,10 @@ 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; |