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i2c: i801: fix potential race in i801_block_transaction_byte_by_byte

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Currently we set SMBHSTCNT_LAST_BYTE only after the host has started
receiving the last byte. If we get e.g. preempted before setting
SMBHSTCNT_LAST_BYTE, the host may be finished with receiving the byte
before SMBHSTCNT_LAST_BYTE is set.
Therefore change the code to set SMBHSTCNT_LAST_BYTE before writing
SMBHSTSTS_BYTE_DONE for the byte before the last byte. Now the code
is also consistent with what we do in i801_isr_byte_done().

Reported-by: Jean Delvare <jdelvare@suse.com>
Closes: https://lore.kernel.org/linux-i2c/20230828152747.09444625@endymion.delvare/
Cc: stable@vger.kernel.org
Acked-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
This commit is contained in:
Heiner Kallweit 2023-09-09 22:25:06 +02:00 committed by Wolfram Sang
parent ce9ecca023
commit f78ca48a8b
1 changed files with 9 additions and 10 deletions
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19
drivers/i2c/busses/i2c-i801.c
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@ -679,15 +679,11 @@ static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
return result ? priv->status : -ETIMEDOUT;
}
if (len == 1 && read_write == I2C_SMBUS_READ)
smbcmd |= SMBHSTCNT_LAST_BYTE;
outb_p(smbcmd | SMBHSTCNT_START, SMBHSTCNT(priv));
for (i = 1; i <= len; i++) {
if (i == len && read_write == I2C_SMBUS_READ)
smbcmd |= SMBHSTCNT_LAST_BYTE;
outb_p(smbcmd, SMBHSTCNT(priv));
if (i == 1)
outb_p(inb(SMBHSTCNT(priv)) | SMBHSTCNT_START,
SMBHSTCNT(priv));
status = i801_wait_byte_done(priv);
if (status)
return status;
@ -710,9 +706,12 @@ static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
data->block[0] = len;
}
/* Retrieve/store value in SMBBLKDAT */
if (read_write == I2C_SMBUS_READ)
if (read_write == I2C_SMBUS_READ) {
data->block[i] = inb_p(SMBBLKDAT(priv));
if (i == len - 1)
outb_p(smbcmd | SMBHSTCNT_LAST_BYTE, SMBHSTCNT(priv));
}
if (read_write == I2C_SMBUS_WRITE && i+1 <= len)
outb_p(data->block[i+1], SMBBLKDAT(priv));