| Message ID | 20240804113611.83613-1-wahrenst@gmx.net |
|---|---|
| State | Accepted |
| Commit | 730bbfaf7d4890bd99e637db7767dc68cfeb24e7 |
| Headers | show |
| Series | spi: spi-fsl-lpspi: Fix scldiv calculation | expand |
On Sun, 04 Aug 2024 13:36:11 +0200, Stefan Wahren wrote: > 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. > > [...] Applied to https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next Thanks! [1/1] spi: spi-fsl-lpspi: Fix scldiv calculation commit: 730bbfaf7d4890bd99e637db7767dc68cfeb24e7 All being well this means that it will be integrated into the linux-next tree (usually sometime in the next 24 hours) and sent to Linus during the next merge window (or sooner if it is a bug fix), however if problems are discovered then the patch may be dropped or reverted. You may get further e-mails resulting from automated or manual testing and review of the tree, please engage with people reporting problems and send followup patches addressing any issues that are reported if needed. If any updates are required or you are submitting further changes they should be sent as incremental updates against current git, existing patches will not be replaced. Please add any relevant lists and maintainers to the CCs when replying to this mail. Thanks, Mark
diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c index 32baa14dfd83..be261ac09df8 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;
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> --- drivers/spi/spi-fsl-lpspi.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) -- 2.34.1