There is nothing to prevent multiple commands being executed simultaneously. Add a mutex to prevent this. Fixes: 606397d67f41 ("fsi: Add ast2600 master driver") Reviewed-by: Joel Stanley <joel@jms.id.au> Reviewed-by: Milton Miller <miltonm@us.ibm.com> Signed-off-by: Eddie James <eajames@linux.ibm.com> Signed-off-by: Joel Stanley <joel@jms.id.au> Link: https://lore.kernel.org/r/20201120004929.185239-1-joel@jms.id.au Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>