cmd: cpu: add release subcommand

Add a new subcommand 'release' to bring up a core to run baremetal
and RTOS applications.

For example on i.MX8M Plus EVK, release the LAST core to run a RTOS
application, passing the sequence number of the CPU core to release,
here it is 3:
    u-boot=> cpu list
      0: cpu@0      NXP i.MX8MP Rev1.1 A53 at 1200 MHz at 31C
      1: cpu@1      NXP i.MX8MP Rev1.1 A53 at 1200 MHz at 30C
      2: cpu@2      NXP i.MX8MP Rev1.1 A53 at 1200 MHz at 31C
      3: cpu@3      NXP i.MX8MP Rev1.1 A53 at 1200 MHz at 31C

    u-boot=> load mmc 1:2 c0000000 /hello_world.bin
    66008 bytes read in 5 ms (12.6 MiB/s)
    u-boot=> dcache flush; icache flush
    u-boot=> cpu release 3 c0000000
    Released CPU core (mpidr: 0x3) to address 0xc0000000

Signed-off-by: Hou Zhiqiang <[email protected]>
Reviewed-by: Simon Glass <[email protected]>

Author: Zhiqiang-Hou

cmd/cpu.c

@@ -3,6 +3,7 @@
  * Copyright (c) 2015 Google, Inc
  * Written by Simon Glass <[email protected]>
  * Copyright (c) 2017 Álvaro Fernández Rojas <[email protected]>
+ * Copyright 2024 NXP
  */
 
 #include <command.h>
@@ -18,6 +19,19 @@ static const char *cpu_feature_name[CPU_FEAT_COUNT] = {
 	"Device ID",
 };
 
+static struct udevice *cpu_find_device(unsigned long cpu_id)
+{
+	struct udevice *dev;
+
+	for (uclass_first_device(UCLASS_CPU, &dev); dev;
+	     uclass_next_device(&dev)) {
+		if (cpu_id == dev_seq(dev))
+			return dev;
+	}
+
+	return NULL;
+}
+
 static int print_cpu_list(bool detail)
 {
 	struct udevice *dev;
@@ -82,10 +96,36 @@ static int do_cpu_detail(struct cmd_tbl *cmdtp, int flag, int argc,
 	return 0;
 }
 
+static int do_cpu_release(struct cmd_tbl *cmdtp, int flag, int argc,
+			  char *const argv[])
+{
+	struct udevice *dev;
+	unsigned long cpu_id;
+	unsigned long long boot_addr;
+
+	if (argc != 3)
+		return CMD_RET_USAGE;
+
+	cpu_id = dectoul(argv[1], NULL);
+	dev = cpu_find_device(cpu_id);
+	if (!dev)
+		return CMD_RET_FAILURE;
+
+	boot_addr = simple_strtoull(argv[2], NULL, 16);
+
+	if (cpu_release_core(dev, boot_addr))
+		return CMD_RET_FAILURE;
+
+	return 0;
+}
+
 U_BOOT_LONGHELP(cpu,
 	"list	- list available CPUs\n"
-	"cpu detail	- show CPU detail");
+	"cpu detail	- show CPU detail\n"
+	"cpu release <core ID> <addr>	- Release CPU <core ID> at <addr>\n"
+	"            <core ID>: the sequence number in list subcommand outputs");
 
 U_BOOT_CMD_WITH_SUBCMDS(cpu, "display information about CPUs", cpu_help_text,
 	U_BOOT_SUBCMD_MKENT(list, 1, 1, do_cpu_list),
-	U_BOOT_SUBCMD_MKENT(detail, 1, 0, do_cpu_detail));
+	U_BOOT_SUBCMD_MKENT(detail, 1, 0, do_cpu_detail),
+	U_BOOT_SUBCMD_MKENT(release, 3, 0, do_cpu_release));