acpi/arm64: Add SBSA Generic Watchdog support in GTDT driver

This driver adds support for parsing SBSA Generic Watchdog timer
in GTDT, parse all info in SBSA Generic Watchdog Structure in GTDT,
and creating a platform device with that information.

This allows the operating system to obtain device data from the
resource of platform device. The platform device named "sbsa-gwdt"
can be used by the ARM SBSA Generic Watchdog driver.
Signed-off-by: Fu Wei <fu.wei@linaro.org>
Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
Tested-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>

drivers/acpi/arm64/gtdt.c

@@ -15,6 +15,7 @@
 #include <linux/init.h>
 #include <linux/irqdomain.h>
 #include <linux/kernel.h>
+#include <linux/platform_device.h>
 
 #include <clocksource/arm_arch_timer.h>
 
@@ -60,6 +61,17 @@ static inline bool is_timer_block(void *platform_timer)
 	return gh->type == ACPI_GTDT_TYPE_TIMER_BLOCK;
 }
 
+static inline bool is_non_secure_watchdog(void *platform_timer)
+{
+	struct acpi_gtdt_header *gh = platform_timer;
+	struct acpi_gtdt_watchdog *wd = platform_timer;
+
+	if (gh->type != ACPI_GTDT_TYPE_WATCHDOG)
+		return false;
+
+	return !(wd->timer_flags & ACPI_GTDT_WATCHDOG_SECURE);
+}
+
 static int __init map_gt_gsi(u32 interrupt, u32 flags)
 {
 	int trigger, polarity;
@@ -312,3 +324,94 @@ int __init acpi_arch_timer_mem_init(struct arch_timer_mem *timer_mem,
 
 	return 0;
 }
+
+/*
+ * Initialize a SBSA generic Watchdog platform device info from GTDT
+ */
+static int __init gtdt_import_sbsa_gwdt(struct acpi_gtdt_watchdog *wd,
+					int index)
+{
+	struct platform_device *pdev;
+	int irq = map_gt_gsi(wd->timer_interrupt, wd->timer_flags);
+
+	/*
+	 * According to SBSA specification the size of refresh and control
+	 * frames of SBSA Generic Watchdog is SZ_4K(Offset 0x000 – 0xFFF).
+	 */
+	struct resource res[] = {
+		DEFINE_RES_MEM(wd->control_frame_address, SZ_4K),
+		DEFINE_RES_MEM(wd->refresh_frame_address, SZ_4K),
+		DEFINE_RES_IRQ(irq),
+	};
+	int nr_res = ARRAY_SIZE(res);
+
+	pr_debug("found a Watchdog (0x%llx/0x%llx gsi:%u flags:0x%x).\n",
+		 wd->refresh_frame_address, wd->control_frame_address,
+		 wd->timer_interrupt, wd->timer_flags);
+
+	if (!(wd->refresh_frame_address && wd->control_frame_address)) {
+		pr_err(FW_BUG "failed to get the Watchdog base address.\n");
+		acpi_unregister_gsi(wd->timer_interrupt);
+		return -EINVAL;
+	}
+
+	if (irq <= 0) {
+		pr_warn("failed to map the Watchdog interrupt.\n");
+		nr_res--;
+	}
+
+	/*
+	 * Add a platform device named "sbsa-gwdt" to match the platform driver.
+	 * "sbsa-gwdt": SBSA(Server Base System Architecture) Generic Watchdog
+	 * The platform driver can get device info below by matching this name.
+	 */
+	pdev = platform_device_register_simple("sbsa-gwdt", index, res, nr_res);
+	if (IS_ERR(pdev)) {
+		acpi_unregister_gsi(wd->timer_interrupt);
+		return PTR_ERR(pdev);
+	}
+
+	return 0;
+}
+
+static int __init gtdt_sbsa_gwdt_init(void)
+{
+	void *platform_timer;
+	struct acpi_table_header *table;
+	int ret, timer_count, gwdt_count = 0;
+
+	if (acpi_disabled)
+		return 0;
+
+	if (ACPI_FAILURE(acpi_get_table(ACPI_SIG_GTDT, 0, &table)))
+		return -EINVAL;
+
+	/*
+	 * Note: Even though the global variable acpi_gtdt_desc has been
+	 * initialized by acpi_gtdt_init() while initializing the arch timers,
+	 * when we call this function to get SBSA watchdogs info from GTDT, the
+	 * pointers stashed in it are stale (since they are early temporary
+	 * mappings carried out before acpi_permanent_mmap is set) and we need
+	 * to re-initialize them with permanent mapped pointer values to let the
+	 * GTDT parsing possible.
+	 */
+	ret = acpi_gtdt_init(table, &timer_count);
+	if (ret || !timer_count)
+		return ret;
+
+	for_each_platform_timer(platform_timer) {
+		if (is_non_secure_watchdog(platform_timer)) {
+			ret = gtdt_import_sbsa_gwdt(platform_timer, gwdt_count);
+			if (ret)
+				break;
+			gwdt_count++;
+		}
+	}
+
+	if (gwdt_count)
+		pr_info("found %d SBSA generic Watchdog(s).\n", gwdt_count);
+
+	return ret;
+}
+
+device_initcall(gtdt_sbsa_gwdt_init);