tpm: provide means of shutting down comms layer while in reset

Currently the Cr50 code resets TPM communications layer at a certain
point during TPM reset process.

It turns out that this is not sufficient - the comms layer keeps
receiving and trying to invoke TPM layer, which does not mesh well
with TPM reset.

Let's provide two callbacks for each comms layer - to shut it down and
to bring it back up. We shut down the comms when starting TPM reset
and bring them back up when reset is completed.

BRANCH=cr50
BUG=b:68012381
TEST=ran AP firmware test suite on both SPI and I2C based devices.

Change-Id: I7caf4a09b9a5c6e5fc6bfe60eae1c0d64ab24904
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/754502
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Mary Ruthven <mruthven@chromium.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/include/tpm_registers.h b/include/tpm_registers.h
index cf7fbe5758..5da9ab6c2f 100644
--- a/include/tpm_registers.h
+++ b/include/tpm_registers.h
@@ -26,9 +26,13 @@ void tpm_register_get(uint32_t regaddr, uint8_t *dest, uint32_t data_size);
 /* Get the current value of the burst size field of the status register. */
 size_t tpm_get_burst_size(void);
 
-/* Register a function to restart TPM communications layer. */
-typedef void (*interface_restart_func)(void);
-void tpm_register_interface(interface_restart_func interface_restart);
+/*
+ * Register functions to start and stop TPM communications layer. The
+ * communications layer should be kept down while TPM is being reset.
+ */
+typedef void (*interface_control_func)(void);
+void tpm_register_interface(interface_control_func interface_start,
+			    interface_control_func interface_stop);
 
 /*
  * This requests the TPM task to reset itself.