i2c: i801: Fix block process call transactions

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>

diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index 3932e8d..2c36b36 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));
        }