apply INT_AP_L extension on I2CS interface

This patch applies INT_AP_L extension on I2CS. It uses
GPIO_MONITOR_I2CS_SDA to detect a transaction start during INT_AP_L
assertion and to deassert INT_AP_L.

BUG=b:148691139
TEST=None

Signed-off-by: Namyoon Woo <namyoon@google.com>
Change-Id: Iedd59b488dfdfaaf71dd71eda6437f1a9402d3c4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2150517
Tested-by: Namyoon Woo <namyoon@chromium.org>
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Commit-Queue: Namyoon Woo <namyoon@chromium.org>

3 files changed, 46 insertions, 13 deletions

diff --git a/board/cr50/gpio.inc b/board/cr50/gpio.inc
index 47c35fb2d2..e527f7815b 100644
--- a/board/cr50/gpio.inc
+++ b/board/cr50/gpio.inc
@@ -110,6 +110,15 @@ GPIO_INT(DETECT_TPM_RST_L_ASSERTED, PIN(1, 4),  GPIO_INT_FALLING,
          tpm_rst_asserted)
 
 /*
+ * A GPIO to sample the current state of the I2CS SDA line, allowing to detect
+ * the 'wedged I2C bus' condition.
+ *
+ * Also, it works to detect an I2C transaction during extended INT_AP_L
+ * assertion.
+ */
+GPIO_INT(MONITOR_I2CS_SDA, PIN(1, 6), GPIO_INT_LOW, i2cs_sda_isr)
+
+/*
  * These GPIOs are to enable or disable EC-CR50 communication.
  * NOTE: If these are changed, you must update the information in board.c
  *       and ec_comm.c
@@ -188,12 +197,6 @@ GPIO(STRAP_B1,        PIN(1, 15), GPIO_INPUT)
 GPIO(UNWEDGE_I2CS_SCL, PIN(1, 5), GPIO_OUT_HIGH)
 
 /*
- * A GPIO to sample the current state of the I2CS SDA line, allowing to detect
- * the 'wedged I2C bus' condition.
- */
-GPIO(MONITOR_I2CS_SDA, PIN(1, 6), GPIO_INPUT)
-
-/*
  * If you change the names of EN_PP3300_INA_L, I2C_SCL_INA, or I2C_SDA_INA,
  * you also need to update the usage in closed_source_set1.c
  */
diff --git a/common/i2cs_tpm.c b/common/i2cs_tpm.c
index cb893cf84f..d76befcbee 100644
--- a/common/i2cs_tpm.c
+++ b/common/i2cs_tpm.c
@@ -84,6 +84,8 @@ static uint32_t i2cs_fifo_adjust_count;
 /* Used to track number of write mismatch errors */
 static uint32_t i2cs_write_error_count;
 
+static bool int_ap_extension_enabled_;
+
 static void process_read_access(uint16_t reg_size,
 				uint16_t tpm_reg, uint8_t *data)
 {
@@ -202,6 +204,11 @@ static void wr_complete_handler(void *i2cs_data, size_t i2cs_data_size)
 		process_write_access(reg_size, tpm_reg,
 				     data, i2cs_data_size);
 
+	if (assert_int_ap()) {
+		gpio_enable_interrupt(GPIO_MONITOR_I2CS_SDA);
+		return;
+	}
+
 	/*
 	 * Since cr50 does not provide i2c clock stretching, we need some
 	 * onther means of flow controlling the host. Let's generate a pulse
@@ -209,20 +216,23 @@ static void wr_complete_handler(void *i2cs_data, size_t i2cs_data_size)
 	 */
 	gpio_set_level(GPIO_INT_AP_L, 0);
 
-	/*
-	 * This is to meet the AP requirement of minimum 4 usec
-	 *  duration of INT_AP_L assertion.
-	 *
-	 * TODO(b/130515803): Ideally, this should be improved
-	 * to support any duration requirement in future.
-	 */
 	tick_delay(2);
 
 	gpio_set_level(GPIO_INT_AP_L, 1);
 }
 
+void i2cs_sda_isr(enum gpio_signal signal)
+{
+	gpio_disable_interrupt(GPIO_MONITOR_I2CS_SDA);
+
+	deassert_int_ap();
+}
+
 static void i2cs_if_stop(void)
 {
+	if (int_ap_extension_enabled_)
+		int_ap_extension_stop_pulse();
+
 	i2cs_register_write_complete_handler(NULL);
 }
 
@@ -231,6 +241,12 @@ static void i2cs_if_start(void)
 	i2cs_register_write_complete_handler(wr_complete_handler);
 }
 
+/* Function that sets up for I2CS to enable INT_AP_L extension. */
+static void i2cs_int_ap_extension_enable_(void)
+{
+	int_ap_extension_enabled_ = true;
+}
+
 static void i2cs_if_register(void)
 {
 	if (!board_tpm_uses_i2c())
@@ -239,6 +255,13 @@ static void i2cs_if_register(void)
 	tpm_register_interface(i2cs_if_start, i2cs_if_stop);
 	i2cs_fifo_adjust_count = 0;
 	i2cs_write_error_count = 0;
+
+	int_ap_register(i2cs_int_ap_extension_enable_);
+
+	/*
+	 * TODO: if TPM_BOARD_CFG has INT_AP extension enabled, then call
+	 * int_ap_extension_enable(), and set int_ap_extension_enabled_ true.
+	 */
 }
 DECLARE_HOOK(HOOK_INIT, i2cs_if_register, HOOK_PRIO_LAST);
 
diff --git a/include/i2c.h b/include/i2c.h
index 4be5472a11..c3fab8a723 100644
--- a/include/i2c.h
+++ b/include/i2c.h
@@ -519,4 +519,11 @@ void i2c_end_xfer_notify(const int port,
 void i2c_trace_notify(int port, uint16_t slave_addr_flags,
 		      int direction, const uint8_t *data, size_t size);
 
+/*
+ * Interrupt handler of GPIO_MONITOR_I2CS_SDA.
+ * Its role is to detect any transaction start during INT_AP_L
+ *  assertion and to deassert INT_AP_L.
+ */
+void i2cs_sda_isr(enum gpio_signal signal);
+
 #endif  /* __CROS_EC_I2C_H */