samus: Add passthru for host commands

Host commands in the range 0x4000-0x7fff will be passed thru the EC to
the PD MCU as 0x0000-0x3fff.

BUG=chrome-os-partner:30079
BRANCH=samus
TEST=manual.  On PD console:
    hcdebug params
  On EC console:
    hostcmd 2 0 -> hex string of EC version
    hostcmd 0x4002 0 -> hex string of PD version, and PD console shows host
      command 2 was received.  The hex response shown on the PD console
      matches the one printed by the EC

Change-Id: Icc2d97c5977145a0c3ad2630d2b5a19e876a36d0
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/207821
Reviewed-by: Bill Richardson <wfrichar@chromium.org>

2 files changed, 55 insertions, 8 deletions

diff --git a/common/host_command.c b/common/host_command.c
index 9f72fe7f43..22374059c6 100644
--- a/common/host_command.c
+++ b/common/host_command.c
@@ -530,18 +530,38 @@ static void host_command_debug_request(struct host_cmd_handler_args *args)
 
 enum ec_status host_command_process(struct host_cmd_handler_args *args)
 {
-	const struct host_command *cmd = find_host_command(args->command);
+	const struct host_command *cmd;
 	enum ec_status rv;
 
 	if (hcdebug)
 		host_command_debug_request(args);
 
-	if (!cmd)
-		rv = EC_RES_INVALID_COMMAND;
-	else if (!(EC_VER_MASK(args->version) & cmd->version_mask))
-		rv = EC_RES_INVALID_VERSION;
-	else
-		rv = cmd->handler(args);
+#ifdef HAS_TASK_PDCMD
+	if (args->command >= EC_CMD_PASSTHRU_OFFSET(1) &&
+	    args->command <= EC_CMD_PASSTHRU_MAX(1)) {
+		rv = pd_host_command(args->command - EC_CMD_PASSTHRU_OFFSET(1),
+				     args->version,
+				     args->params, args->params_size,
+				     args->response, args->response_max);
+		if (rv >= 0) {
+			/* Success; store actual response size */
+			args->response_size = rv;
+			rv = EC_SUCCESS;
+		} else {
+			/* Failure, returned as negative error code */
+			rv = -rv;
+		}
+	} else
+#endif
+	{
+		cmd = find_host_command(args->command);
+		if (!cmd)
+			rv = EC_RES_INVALID_COMMAND;
+		else if (!(EC_VER_MASK(args->version) & cmd->version_mask))
+			rv = EC_RES_INVALID_VERSION;
+		else
+			rv = cmd->handler(args);
+	}
 
 	if (rv != EC_RES_SUCCESS)
 		CPRINTS("HC err %d", rv);
diff --git a/include/ec_commands.h b/include/ec_commands.h
index d867c31dc1..7233d43bd3 100644
--- a/include/ec_commands.h
+++ b/include/ec_commands.h
@@ -500,7 +500,7 @@ struct ec_host_response {
 /*
  * Notes on commands:
  *
- * Each command is an 8-byte command value.  Commands which take params or
+ * Each command is an 16-bit command value.  Commands which take params or
  * return response data specify structs for that data.  If no struct is
  * specified, the command does not input or output data, respectively.
  * Parameter/response length is implicit in the structs.  Some underlying
@@ -2502,6 +2502,33 @@ struct ec_response_pd_status {
 
 /*****************************************************************************/
 /*
+ * Passthru commands
+ *
+ * Some platforms have sub-processors chained to each other.  For example.
+ *
+ *     AP <--> EC <--> PD MCU
+ *
+ * The top 2 bits of the command number are used to indicate which device the
+ * command is intended for.  Device 0 is always the device receiving the
+ * command; other device mapping is board-specific.
+ *
+ * When a device receives a command to be passed to a sub-processor, it passes
+ * it on with the device number set back to 0.  This allows the sub-processor
+ * to remain blissfully unaware of whether the command originated on the next
+ * device up the chain, or was passed through from the AP.
+ *
+ * In the above example, if the AP wants to send command 0x0002 to the PD MCU,
+ *     AP sends command 0x4002 to the EC
+ *     EC sends command 0x0002 to the PD MCU
+ *     EC forwards PD MCU response back to the AP
+ */
+
+/* Offset and max command number for sub-device n */
+#define EC_CMD_PASSTHRU_OFFSET(n) (0x4000 * (n))
+#define EC_CMD_PASSTHRU_MAX(n) (EC_CMD_PASSTHRU_OFFSET(n) + 0x3fff)
+
+/*****************************************************************************/
+/*
  * Deprecated constants. These constants have been renamed for clarity. The
  * meaning and size has not changed. Programs that use the old names should
  * switch to the new names soon, as the old names may not be carried forward