LoongArch: Add ACPI standard hardware register based S3 support

Most LoongArch 64 machines are using custom "SADR" ACPI extension to
perform ACPI S3 sleep. However the standard ACPI way to perform sleep
is to write a value to ACPI PM1/SLEEP_CTL register, and this is never
supported properly in kernel.

Add standard S3 sleep by providing a default DoSuspend function which
calls ACPI's acpi_enter_sleep_state() routine when SADR is not provided
by the firmware.

Also fix suspend assembly code so that ra is set properly before go
into sleep routine. (Previously linked address of jirl was set to a0,
some firmware do require return address in a0 but it's already set with
la.pcrel before).
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/power/platform.c

@@ -49,22 +49,34 @@ static int __init loongson_cpufreq_init(void)
 
 arch_initcall(loongson_cpufreq_init);
 
+static void default_suspend_addr(void)
+{
+	acpi_enter_sleep_state(ACPI_STATE_S3);
+}
+
 static int __init loongson3_acpi_suspend_init(void)
 {
 #ifdef CONFIG_ACPI
 	acpi_status status;
 	uint64_t suspend_addr = 0;
 
-	if (acpi_disabled || acpi_gbl_reduced_hardware)
+	if (acpi_disabled)
+		return 0;
+
+	if (!acpi_gbl_reduced_hardware)
+		acpi_write_bit_register(ACPI_BITREG_SCI_ENABLE, 1);
+
+	if (!acpi_sleep_state_supported(ACPI_STATE_S3))
 		return 0;
 
-	acpi_write_bit_register(ACPI_BITREG_SCI_ENABLE, 1);
 	status = acpi_evaluate_integer(NULL, "\\SADR", NULL, &suspend_addr);
 	if (ACPI_FAILURE(status) || !suspend_addr) {
-		pr_err("ACPI S3 is not support!\n");
-		return -1;
+		pr_info("ACPI S3 supported with hardware register default\n");
+		loongson_sysconf.suspend_addr = (u64)default_suspend_addr;
+	} else {
+		pr_info("ACPI S3 supported with Loongson ACPI SADR extension\n");
+		loongson_sysconf.suspend_addr = (u64)phys_to_virt(PHYSADDR(suspend_addr));
 	}
-	loongson_sysconf.suspend_addr = (u64)phys_to_virt(PHYSADDR(suspend_addr));
 #endif
 	return 0;
 }

arch/loongarch/power/suspend_asm.S

@@ -66,7 +66,7 @@ SYM_FUNC_START(loongarch_suspend_enter)
 	la.pcrel	a0, loongarch_wakeup_start
 	la.pcrel	t0, loongarch_suspend_addr
 	ld.d		t0, t0, 0
-	jirl		a0, t0, 0 /* Call BIOS's STR sleep routine */
+	jirl		ra, t0, 0 /* Call BIOS's STR sleep routine */
 
 	/*
 	 * This is where we return upon wakeup.