i2cs: reset local variables when reinitializing.

When tpm is reset the i2c slave interface initialization function is
called, but it does not quite re-initialize the interface.

This patch adds both a hardware pulse to make sure that the i2c slave
interface state machine is set into the initial state, and code to
zero static variables of the driver.

BRANCH=none
BUG=none
TEST=with the change on the AP firmware side which prevents losing i2c
     ready interrupts early in the process tpm reset became much more
     reliable. Resetting from EC, AP of cr50 consoles reliably
     restarts reef without any TPM communications problems.

Change-Id: I604607c32d4dfc554b245d3d3d82b9ad38271962
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/392306
Reviewed-by: Scott Collyer <scollyer@chromium.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/chip/g/i2cs.c b/chip/g/i2cs.c
index 507fbfcb1a..7cced88fcc 100644
--- a/chip/g/i2cs.c
+++ b/chip/g/i2cs.c
@@ -105,6 +105,23 @@ static void i2cs_init(void)
 
 	pmu_clock_en(PERIPH_I2CS);
 
+	/*
+	 * Toggle the reset register to make sure i2cs interface is in the
+	 * initial state even if it is mid transaction at this time.
+	 */
+	GWRITE_FIELD(PMU, RST0, DI2CS0, 1);
+
+	/*
+	 * This initialization is guraranteed to take way more than enough
+	 * time for the reset to kick in.
+	 */
+	memset(i2cs_buffer, 0, sizeof(i2cs_buffer));
+	last_write_pointer = 0;
+	last_read_pointer = 0;
+
+	GWRITE_FIELD(PMU, RST0, DI2CS0, 0);
+
+
 	/* Set pinmux registers for I2CS interface */
 	i2cs_set_pinmux();