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>

3 files changed, 18 insertions, 5 deletions

diff --git a/chip/g/i2cs.c b/chip/g/i2cs.c
index 8c00c4ddea..0cd5abf13f 100644
--- a/chip/g/i2cs.c
+++ b/chip/g/i2cs.c
@@ -351,6 +351,10 @@ void i2cs_post_read_fill_fifo(uint8_t *buffer, size_t len)
 int i2cs_register_write_complete_handler(wr_complete_handler_f wc_handler)
 {
 	task_disable_irq(GC_IRQNUM_I2CS0_INTR_WRITE_COMPLETE_INT);
+
+	if (!wc_handler)
+		return 0;
+
 	i2cs_init();
 	write_complete_handler_ = wc_handler;
 	task_enable_irq(GC_IRQNUM_I2CS0_INTR_WRITE_COMPLETE_INT);
diff --git a/chip/g/sps.c b/chip/g/sps.c
index 6a5fed0ee3..fc7a0d8458 100644
--- a/chip/g/sps.c
+++ b/chip/g/sps.c
@@ -215,6 +215,9 @@ int sps_register_rx_handler(enum sps_mode mode, rx_handler_f rx_handler,
 	task_disable_irq(GC_IRQNUM_SPS0_RXFIFO_LVL_INTR);
 	task_disable_irq(GC_IRQNUM_SPS0_CS_DEASSERT_INTR);
 
+	if (!rx_handler)
+		return 0;
+
 	if (!rx_fifo_threshold)
 		rx_fifo_threshold = 8;  /* This is a sensible default. */
 	sps_rx_handler = rx_handler;
diff --git a/chip/g/sps_tpm.c b/chip/g/sps_tpm.c
index 1d7706e432..5d5073bb6f 100644
--- a/chip/g/sps_tpm.c
+++ b/chip/g/sps_tpm.c
@@ -265,14 +265,20 @@ static void tpm_rx_handler(uint8_t *data, size_t data_size, int cs_disabled)
 		init_new_cycle();
 }
 
-static void sps_tpm_enable(void)
+static void sps_if_stop(void)
+{
+	/* Let's shut down the interface while TPM is being reset. */
+	sps_register_rx_handler(0, NULL, 0);
+}
+
+static void sps_if_start(void)
 {
 	/*
-	 * Let's make sure we get an interrupt as soon as the header is
-	 * received.
+	 * Threshold of 3 makes sure we get an interrupt as soon as the header
+	 * is received.
 	 */
-	sps_register_rx_handler(SPS_GENERIC_MODE, tpm_rx_handler, 3);
 	init_new_cycle();
+	sps_register_rx_handler(SPS_GENERIC_MODE, tpm_rx_handler, 3);
 }
 
 
@@ -281,6 +287,6 @@ static void sps_if_register(void)
 	if (!board_tpm_uses_spi())
 		return;
 
-	tpm_register_interface(sps_tpm_enable);
+	tpm_register_interface(sps_if_start, sps_if_stop);
 }
 DECLARE_HOOK(HOOK_INIT, sps_if_register, HOOK_PRIO_LAST);