linux-kernel - [PATCH AUTOSEL 6.12 02/23] spi: spi-fsl-lpspi: Adjust type of scldiv

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Message-ID: <20241124124919.3338752-2-sashal@kernel.org>
Date: Sun, 24 Nov 2024 07:48:13 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Stefan Wahren <wahrenst@....net>,
	Frank Li <Frank.Li@....com>,
	Mark Brown <broonie@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	linux-spi@...r.kernel.org,
	imx@...ts.linux.dev
Subject: [PATCH AUTOSEL 6.12 02/23] spi: spi-fsl-lpspi: Adjust type of scldiv

From: Stefan Wahren <wahrenst@....net>

[ 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@....net>
Reviewed-by: Frank Li <Frank.Li@....com>
Link: https://patch.msgid.link/20240930093056.93418-2-wahrenst@gmx.net
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 977e8b55c82b7..196cc68f2057b 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),
-- 
2.43.0