tools/power/x86/intel-speed-select: Add retries for mail box commands

Retry mail box command on failure. The default retry count is 3. This can
be changed by "-r|--retry" options. This helps during early bring up of
platforms.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>

tools/power/x86/intel-speed-select/isst-config.c

@@ -45,6 +45,7 @@ static int auto_mode;
 static int fact_enable_fail;
 
 static int mbox_delay;
+static int mbox_retries = 3;
 
 /* clos related */
 static int current_clos = -1;
@@ -738,7 +739,7 @@ int isst_send_mbox_command(unsigned int cpu, unsigned char command,
 			   unsigned int req_data, unsigned int *resp)
 {
 	const char *pathname = "/dev/isst_interface";
-	int fd;
+	int fd, retry;
 	struct isst_if_mbox_cmds mbox_cmds = { 0 };
 
 	debug_printf(
@@ -797,25 +798,35 @@ int isst_send_mbox_command(unsigned int cpu, unsigned char command,
 	if (fd < 0)
 		err(-1, "%s open failed", pathname);
 
-	if (ioctl(fd, ISST_IF_MBOX_COMMAND, &mbox_cmds) == -1) {
-		if (errno == ENOTTY) {
-			perror("ISST_IF_MBOX_COMMAND\n");
-			fprintf(stderr, "Check presence of kernel modules: isst_if_mbox_pci or isst_if_mbox_msr\n");
-			exit(0);
+	retry = mbox_retries;
+
+	do {
+		if (ioctl(fd, ISST_IF_MBOX_COMMAND, &mbox_cmds) == -1) {
+			if (errno == ENOTTY) {
+				perror("ISST_IF_MBOX_COMMAND\n");
+				fprintf(stderr, "Check presence of kernel modules: isst_if_mbox_pci or isst_if_mbox_msr\n");
+				exit(0);
+			}
+			debug_printf(
+				"Error: mbox_cmd cpu:%d command:%x sub_command:%x parameter:%x req_data:%x errorno:%d\n",
+				cpu, command, sub_command, parameter, req_data, errno);
+			--retry;
+		} else {
+			*resp = mbox_cmds.mbox_cmd[0].resp_data;
+			debug_printf(
+				"mbox_cmd response: cpu:%d command:%x sub_command:%x parameter:%x req_data:%x resp:%x\n",
+				cpu, command, sub_command, parameter, req_data, *resp);
+			break;
 		}
-		debug_printf(
-			"Error: mbox_cmd cpu:%d command:%x sub_command:%x parameter:%x req_data:%x errorno:%d\n",
-			cpu, command, sub_command, parameter, req_data, errno);
-		return -1;
-	} else {
-		*resp = mbox_cmds.mbox_cmd[0].resp_data;
-		debug_printf(
-			"mbox_cmd response: cpu:%d command:%x sub_command:%x parameter:%x req_data:%x resp:%x\n",
-			cpu, command, sub_command, parameter, req_data, *resp);
-	}
+	} while (retry);
 
 	close(fd);
 
+	if (!retry) {
+		debug_printf("Failed mbox command even after retries\n");
+		return -1;
+
+	}
 	return 0;
 }
 
@@ -2605,6 +2616,7 @@ static void usage(void)
 	printf("\t[-o|--out] : Output file\n");
 	printf("\t\t\tDefault : stderr\n");
 	printf("\t[-p|--pause] : Delay between two mail box commands in milliseconds\n");
+	printf("\t[-r|--retry] : Retry count for mail box commands on failure, default 3\n");
 	printf("\t[-v|--version] : Print version\n");
 
 	printf("\nResult format\n");
@@ -2650,6 +2662,7 @@ static void cmdline(int argc, char **argv)
 		{ "info", no_argument, 0, 'i' },
 		{ "pause", required_argument, 0, 'p' },
 		{ "out", required_argument, 0, 'o' },
+		{ "retry", required_argument, 0, 'r' },
 		{ "version", no_argument, 0, 'v' },
 		{ 0, 0, 0, 0 }
 	};
@@ -2709,6 +2722,13 @@ static void cmdline(int argc, char **argv)
 			else
 				mbox_delay = ret;
 			break;
+		case 'r':
+			ret = strtol(optarg, &ptr, 10);
+			if (!ret)
+				fprintf(stderr, "Invalid retry count, ignore\n");
+			else
+				mbox_retries = ret;
+			break;
 		case 'v':
 			print_version();
 			break;