linux-kernel - [PATCH] spi: bcm63xx: fix max prepend length

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Message-Id: <20230629071453.62024-1-jonas.gorski@gmail.com>
Date:   Thu, 29 Jun 2023 09:14:52 +0200
From:   Jonas Gorski <jonas.gorski@...il.com>
To:     Mark Brown <broonie@...nel.org>,
        Grant Likely <grant.likely@...retlab.ca>
Cc:     linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] spi: bcm63xx: fix max prepend length

The command word is defined as following:

    /* Command */
    #define SPI_CMD_COMMAND_SHIFT           0
    #define SPI_CMD_DEVICE_ID_SHIFT         4
    #define SPI_CMD_PREPEND_BYTE_CNT_SHIFT  8
    #define SPI_CMD_ONE_BYTE_SHIFT          11
    #define SPI_CMD_ONE_WIRE_SHIFT          12

If the prepend byte count field starts at bit 8, and the next defined
bit is SPI_CMD_ONE_BYTE at bit 11, it can be at most 3 bits wide, and
thus the max value is 7, not 15.

Fixes: b17de076062a ("spi/bcm63xx: work around inability to keep CS up")
Signed-off-by: Jonas Gorski <jonas.gorski@...il.com>
---
 drivers/spi/spi-bcm63xx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-bcm63xx.c b/drivers/spi/spi-bcm63xx.c
index 9aecb77c3d89..07b5b71b2352 100644
--- a/drivers/spi/spi-bcm63xx.c
+++ b/drivers/spi/spi-bcm63xx.c
@@ -126,7 +126,7 @@ enum bcm63xx_regs_spi {
 	SPI_MSG_DATA_SIZE,
 };
 
-#define BCM63XX_SPI_MAX_PREPEND		15
+#define BCM63XX_SPI_MAX_PREPEND		7
 
 #define BCM63XX_SPI_MAX_CS		8
 #define BCM63XX_SPI_BUS_NUM		0
-- 
2.34.1