i2c: i801: Fix block process call transactions

[ Upstream commit c1c9d0f6f7f1dbf29db996bd8e166242843a5f21 ]

According to the Intel datasheets, software must reset the block
buffer index twice for block process call transactions: once before
writing the outgoing data to the buffer, and once again before
reading the incoming data from the buffer.

The driver is currently missing the second reset, causing the wrong
portion of the block buffer to be read.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Reported-by: Piotr Zakowski <piotr.zakowski@intel.com>
Closes: https://lore.kernel.org/linux-i2c/20240213120553.7b0ab120@endymion.delvare/
Fixes: 315cd67c9453 ("i2c: i801: Add Block Write-Block Read Process Call support")
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index 070999139c6dcbe24ddde994543cf1ec9df74e82..6a5a93cf4ecc6413b1d0018ad782a053a0a8f825 100644 (file)
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -498,11 +498,10 @@ static int i801_block_transaction_by_block(struct i801_priv *priv,
        /* Set block buffer mode */
        outb_p(inb_p(SMBAUXCTL(priv)) | SMBAUXCTL_E32B, SMBAUXCTL(priv));
 
-       inb_p(SMBHSTCNT(priv)); /* reset the data buffer index */
-
        if (read_write == I2C_SMBUS_WRITE) {
                len = data->block[0];
                outb_p(len, SMBHSTDAT0(priv));
+               inb_p(SMBHSTCNT(priv)); /* reset the data buffer index */
                for (i = 0; i < len; i++)
                        outb_p(data->block[i+1], SMBBLKDAT(priv));
        }
@@ -520,6 +519,7 @@ static int i801_block_transaction_by_block(struct i801_priv *priv,
                }
 
                data->block[0] = len;
+               inb_p(SMBHSTCNT(priv)); /* reset the data buffer index */
                for (i = 0; i < len; i++)
                        data->block[i + 1] = inb_p(SMBBLKDAT(priv));
        }