system: Add support for emulated sysrq

On keyboard-less design, we will implement a special debug mode,
based on button sequences, to transmit sysrq events to the AP.

This implements the new MKBP event to send sysrq, and a console
command to test it. Later CL will implement debug mode itself.

BRANCH=none
BUG=b:35775099
TEST=sysrq available in EC console
TEST=sysrq h => help message in AP console
TEST=sysrq b => AP reboots

Change-Id: I71d3f77497baf8cc7fac65cd040ce20513b507bc
Reviewed-on: https://chromium-review.googlesource.com/456520
Commit-Ready: Nicolas Boichat <drinkcat@chromium.org>
Tested-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Aseda Aboagye <aaboagye@chromium.org>

5 files changed, 51 insertions, 0 deletions

diff --git a/common/keyboard_mkbp.c b/common/keyboard_mkbp.c
index 277e63dc03..e592addf2f 100644
--- a/common/keyboard_mkbp.c
+++ b/common/keyboard_mkbp.c
@@ -90,6 +90,7 @@ static int get_data_size(enum ec_mkbp_event e)
 	case EC_MKBP_EVENT_HOST_EVENT:
 	case EC_MKBP_EVENT_BUTTON:
 	case EC_MKBP_EVENT_SWITCH:
+	case EC_MKBP_EVENT_SYSRQ:
 		return sizeof(uint32_t);
 	default:
 		/* For unknown types, say it's 0. */
@@ -258,6 +259,15 @@ void keyboard_update_button(enum keyboard_button_type button, int is_pressed)
 		      (const uint8_t *)&mkbp_button_state);
 }
 
+#ifdef CONFIG_EMULATED_SYSRQ
+void send_sysrq(uint8_t key)
+{
+	uint32_t value = key;
+
+	mkbp_fifo_add(EC_MKBP_EVENT_SYSRQ, (const uint8_t *)&value);
+}
+#endif
+
 #ifdef CONFIG_POWER_BUTTON
 /**
  * Handle power button changing state.
@@ -325,6 +335,14 @@ static int switch_get_next_event(uint8_t *out)
 }
 DECLARE_EVENT_SOURCE(EC_MKBP_EVENT_SWITCH, switch_get_next_event);
 
+#ifdef CONFIG_EMULATED_SYSRQ
+static int sysrq_get_next_event(uint8_t *out)
+{
+	return get_next_event(out, EC_MKBP_EVENT_SYSRQ);
+}
+DECLARE_EVENT_SOURCE(EC_MKBP_EVENT_SYSRQ, sysrq_get_next_event);
+#endif
+
 void keyboard_send_battery_key(void)
 {
 	uint8_t state[KEYBOARD_COLS];
diff --git a/common/system.c b/common/system.c
index 72d642f0f4..e152696941 100644
--- a/common/system.c
+++ b/common/system.c
@@ -1109,6 +1109,23 @@ DECLARE_CONSOLE_COMMAND(jumptags, command_jumptags,
 			"List jump tags");
 #endif /* CONFIG_CMD_JUMPTAGS */
 
+#ifdef CONFIG_EMULATED_SYSRQ
+static int command_sysrq(int argc, char **argv)
+{
+	char key = 'x';
+
+	if (argc > 1 && argv[1])
+		key = argv[1][0];
+
+	send_sysrq(key);
+
+	return EC_SUCCESS;
+}
+DECLARE_CONSOLE_COMMAND(sysrq, command_sysrq,
+			"[key]",
+			"Simulate sysrq press (default: x)");
+#endif /* CONFIG_EMULATED_SYSRQ */
+
 /*****************************************************************************/
 /* Host commands */
 
diff --git a/include/config.h b/include/config.h
index d096c90c2c..fcf98ada97 100644
--- a/include/config.h
+++ b/include/config.h
@@ -922,6 +922,9 @@
 /* Support EC chip internal data EEPROM */
 #undef CONFIG_EEPROM
 
+/* Support for sending emulated sysrq commands to AP */
+#undef CONFIG_EMULATED_SYSRQ
+
 /* Support for eSPI for host communication */
 #undef CONFIG_ESPI
 
diff --git a/include/ec_commands.h b/include/ec_commands.h
index 08decc71a6..d10fca9df5 100644
--- a/include/ec_commands.h
+++ b/include/ec_commands.h
@@ -2797,6 +2797,9 @@ enum ec_mkbp_event {
 	/* New Fingerprint sensor event, the event data is fp_events bitmap. */
 	EC_MKBP_EVENT_FINGERPRINT = 5,
 
+	/* Sysrq event */
+	EC_MKBP_EVENT_SYSRQ = 6,
+
 	/* Number of MKBP events */
 	EC_MKBP_EVENT_COUNT,
 };
@@ -2818,6 +2821,8 @@ union __ec_align_offset1 ec_response_get_next_data {
 	uint32_t switches;
 
 	uint32_t fp_events;
+
+	uint32_t sysrq;
 };
 
 struct __ec_align1 ec_response_get_next_event {
diff --git a/include/system.h b/include/system.h
index b584e3586e..38132140b5 100644
--- a/include/system.h
+++ b/include/system.h
@@ -498,4 +498,12 @@ uintptr_t system_get_fw_reset_vector(uintptr_t base);
  */
 int system_is_reboot_warm(void);
 
+/*
+ * Sends an emulated sysrq to the host, used by button-based debug mode.
+ * Only implemented on top of MKBP protocol.
+ *
+ * @param key		Key to be sent (e.g. 'x')
+ */
+void send_sysrq(uint8_t key);
+
 #endif  /* __CROS_EC_SYSTEM_H */