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, 2 deletions

diff --git a/common/i2cs_tpm.c b/common/i2cs_tpm.c
index 42089681dd..4518eddbb9 100644
--- a/common/i2cs_tpm.c
+++ b/common/i2cs_tpm.c
@@ -211,7 +211,12 @@ static void wr_complete_handler(void *i2cs_data, size_t i2cs_data_size)
 	gpio_set_level(GPIO_INT_AP_L, 1);
 }
 
-static void i2cs_tpm_enable(void)
+static void i2cs_if_stop(void)
+{
+	i2cs_register_write_complete_handler(NULL);
+}
+
+static void i2cs_if_start(void)
 {
 	i2cs_register_write_complete_handler(wr_complete_handler);
 }
@@ -221,7 +226,7 @@ static void i2cs_if_register(void)
 	if (!board_tpm_uses_i2c())
 		return;
 
-	tpm_register_interface(i2cs_tpm_enable);
+	tpm_register_interface(i2cs_if_start, i2cs_if_stop);
 	i2cs_fifo_adjust_count = 0;
 	i2cs_write_error_count = 0;
 }