tpm: only attempt to disable the LPC CLKRUN if is already enabled
authorJavier Martinez Canillas <javierm@redhat.com>
Mon, 25 Dec 2017 02:22:51 +0000 (03:22 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 15 Mar 2018 09:54:25 +0000 (10:54 +0100)
commit7b6f41b7377ad4c6a17b860bb60f13d1b42cff7d
tree5ce67b58158c8715738a684d7e800c69a3e6b14c
parent30c3b70e8d839a926e29dc1db6ba9c1b4deac1d8
tpm: only attempt to disable the LPC CLKRUN if is already enabled

commit 6c9f0ce0dffe64da2204f38b0fd90f3ae2a8903c upstream.

Commit 5e572cab92f0 ("tpm: Enable CLKRUN protocol for Braswell systems")
added logic in the TPM TIS driver to disable the Low Pin Count CLKRUN
signal during TPM transactions.

Unfortunately this breaks other devices that are attached to the LPC bus
like for example PS/2 mouse and keyboards.

One flaw with the logic is that it assumes that the CLKRUN is always
enabled, and so it unconditionally enables it after a TPM transaction.

But it could be that the CLKRUN# signal was already disabled in the LPC
bus and so after the driver probes, CLKRUN_EN will remain enabled which
may break other devices that are attached to the LPC bus but don't have
support for the CLKRUN protocol.

Fixes: 5e572cab92f0 ("tpm: Enable CLKRUN protocol for Braswell systems")
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Tested-by: James Ettle <james@ettle.org.uk>
Tested-by: Jeffery Miller <jmiller@neverware.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/char/tpm/tpm_tis_core.c