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

[ Upstream commit fa8ecda9876ac1e7b29257aa82af1fd0695496e2 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c
index 9573b8fa4fbfc63c4af7b247bc951cf5ccc5b537..29b9676fe43d89cd9ba99c9878ad364400ecc793 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),