ACPI / sysfs: Provide quirk mechanism to prevent GPE flooding

Sometimes, the users may require a quirk to be provided from ACPI subsystem
core to prevent a GPE from flooding.
Normally, if a GPE cannot be dispatched, ACPICA core automatically prevents
the GPE from firing. But there are cases the GPE is dispatched by _Lxx/_Exx
provided via AML table, and OSPM is lacking of the knowledge to get
_Lxx/_Exx correctly executed to handle the GPE, thus the GPE flooding may
still occur.

The existing quirk mechanism can be enabled/disabled using the following
commands to prevent such kind of GPE flooding during runtime:
 # echo mask > /sys/firmware/acpi/interrupts/gpe00
 # echo unmask > /sys/firmware/acpi/interrupts/gpe00
To avoid GPE flooding during boot, we need a boot stage mechanism.

This patch provides such a boot stage quirk mechanism to stop this kind of
GPE flooding. This patch doesn't fix any feature gap but since the new
feature gaps could be found in the future endlessly, and can disappear if
the feature gaps are filled, providing a boot parameter rather than a DMI
table should suffice.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=53071
Link: https://bugzilla.kernel.org/show_bug.cgi?id=117481
Link: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/887793
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -106,6 +106,16 @@
 			use by PCI
 			Format: <irq>,<irq>...
 
+	acpi_mask_gpe=  [HW,ACPI]
+			Due to the existence of _Lxx/_Exx, some GPEs triggered
+			by unsupported hardware/firmware features can result in
+                        GPE floodings that cannot be automatically disabled by
+                        the GPE dispatcher.
+			This facility can be used to prevent such uncontrolled
+			GPE floodings.
+			Format: <int>
+			Support masking of GPEs numbered from 0x00 to 0x7f.
+
 	acpi_no_auto_serialize	[HW,ACPI]
 			Disable auto-serialization of AML methods
 			AML control methods that contain the opcodes to create

drivers/acpi/internal.h

@@ -37,6 +37,7 @@ void acpi_amba_init(void);
 static inline void acpi_amba_init(void) {}
 #endif
 int acpi_sysfs_init(void);
+void acpi_gpe_apply_masked_gpes(void);
 void acpi_container_init(void);
 void acpi_memory_hotplug_init(void);
 #ifdef	CONFIG_ACPI_HOTPLUG_IOAPIC

drivers/acpi/scan.c

@@ -2074,6 +2074,7 @@ int __init acpi_scan_init(void)
 		}
 	}
 
+	acpi_gpe_apply_masked_gpes();
 	acpi_update_all_gpes();
 	acpi_ec_ecdt_start();
 

drivers/acpi/sysfs.c

@@ -708,6 +708,62 @@ end:
 	return result ? result : size;
 }
 
+/*
+ * A Quirk Mechanism for GPE Flooding Prevention:
+ *
+ * Quirks may be needed to prevent GPE flooding on a specific GPE. The
+ * flooding typically cannot be detected and automatically prevented by
+ * ACPI_GPE_DISPATCH_NONE check because there is a _Lxx/_Exx prepared in
+ * the AML tables. This normally indicates a feature gap in Linux, thus
+ * instead of providing endless quirk tables, we provide a boot parameter
+ * for those who want this quirk. For example, if the users want to prevent
+ * the GPE flooding for GPE 00, they need to specify the following boot
+ * parameter:
+ *   acpi_mask_gpe=0x00
+ * The masking status can be modified by the following runtime controlling
+ * interface:
+ *   echo unmask > /sys/firmware/acpi/interrupts/gpe00
+ */
+
+/*
+ * Currently, the GPE flooding prevention only supports to mask the GPEs
+ * numbered from 00 to 7f.
+ */
+#define ACPI_MASKABLE_GPE_MAX	0x80
+
+static u64 __initdata acpi_masked_gpes;
+
+static int __init acpi_gpe_set_masked_gpes(char *val)
+{
+	u8 gpe;
+
+	if (kstrtou8(val, 0, &gpe) || gpe > ACPI_MASKABLE_GPE_MAX)
+		return -EINVAL;
+	acpi_masked_gpes |= ((u64)1<<gpe);
+
+	return 1;
+}
+__setup("acpi_mask_gpe=", acpi_gpe_set_masked_gpes);
+
+void __init acpi_gpe_apply_masked_gpes(void)
+{
+	acpi_handle handle;
+	acpi_status status;
+	u8 gpe;
+
+	for (gpe = 0;
+	     gpe < min_t(u8, ACPI_MASKABLE_GPE_MAX, acpi_current_gpe_count);
+	     gpe++) {
+		if (acpi_masked_gpes & ((u64)1<<gpe)) {
+			status = acpi_get_gpe_device(gpe, &handle);
+			if (ACPI_SUCCESS(status)) {
+				pr_info("Masking GPE 0x%x.\n", gpe);
+				(void)acpi_mask_gpe(handle, gpe, TRUE);
+			}
+		}
+	}
+}
+
 void acpi_irq_stats_init(void)
 {
 	acpi_status status;