| Message ID | 20240930093056.93418-2-wahrenst@gmx.net (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | spi: spi-fsl-lpspi: Some calculation improvements | expand |
On Mon, Sep 30, 2024 at 11:30:54AM +0200, Stefan Wahren wrote: > The target value of scldiv is just a byte, but its calculation in > fsl_lpspi_set_bitrate could be negative. So use an adequate type to store > the result and avoid overflows. After that this needs range check > adjustments, but this should make the code less opaque. > > Signed-off-by: Stefan Wahren <wahrenst@gmx.net> > --- Reviewed-by: Frank Li <Frank.Li@nxp.com> > drivers/spi/spi-fsl-lpspi.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c > index 977e8b55c82b..196cc68f2057 100644 > --- a/drivers/spi/spi-fsl-lpspi.c > +++ b/drivers/spi/spi-fsl-lpspi.c > @@ -315,9 +315,10 @@ 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, div; > + unsigned int perclk_rate, div; > u8 prescale_max; > u8 prescale; > + int scldiv; > > perclk_rate = clk_get_rate(fsl_lpspi->clk_per); > prescale_max = fsl_lpspi->devtype_data->prescale_max; > @@ -338,13 +339,13 @@ static int fsl_lpspi_set_bitrate(struct fsl_lpspi_data *fsl_lpspi) > > for (prescale = 0; prescale <= prescale_max; prescale++) { > scldiv = div / (1 << prescale) - 2; > - if (scldiv < 256) { > + if (scldiv >= 0 && scldiv < 256) { > fsl_lpspi->config.prescale = prescale; > break; > } > } > > - if (scldiv >= 256) > + if (scldiv < 0 || scldiv >= 256) > return -EINVAL; > > writel(scldiv | (scldiv << 8) | ((scldiv >> 1) << 16), > -- > 2.34.1 >
diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c index 977e8b55c82b..196cc68f2057 100644 --- a/drivers/spi/spi-fsl-lpspi.c +++ b/drivers/spi/spi-fsl-lpspi.c @@ -315,9 +315,10 @@ 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, div; + unsigned int perclk_rate, div; u8 prescale_max; u8 prescale; + int scldiv; perclk_rate = clk_get_rate(fsl_lpspi->clk_per); prescale_max = fsl_lpspi->devtype_data->prescale_max; @@ -338,13 +339,13 @@ static int fsl_lpspi_set_bitrate(struct fsl_lpspi_data *fsl_lpspi) for (prescale = 0; prescale <= prescale_max; prescale++) { scldiv = div / (1 << prescale) - 2; - if (scldiv < 256) { + if (scldiv >= 0 && scldiv < 256) { fsl_lpspi->config.prescale = prescale; break; } } - if (scldiv >= 256) + if (scldiv < 0 || scldiv >= 256) return -EINVAL; writel(scldiv | (scldiv << 8) | ((scldiv >> 1) << 16),
The target value of scldiv is just a byte, but its calculation in fsl_lpspi_set_bitrate could be negative. So use an adequate type to store the result and avoid overflows. After that this needs range check adjustments, but this should make the code less opaque. Signed-off-by: Stefan Wahren <wahrenst@gmx.net> --- drivers/spi/spi-fsl-lpspi.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) -- 2.34.1