spi: spi-fsl-lpspi: Adjust type of scldiv

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>
Link: https://patch.msgid.link/20240930093056.93418-2-wahrenst@gmx.net
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c
index 977e8b55c82b7ddc1dc1b05c41cfc838c93b40e0..196cc68f2057ba7027ae67a394c3ec0ffc0ebfad 100644 (file)
--- 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),