ACPI fixes for 4.17-rc3

- Change the ACPI subsystem initialization ordering to initialize
    the WDAT watchodg before reserving PNP motherboard resources so
    as to allow the watchdog to allocate its resources before the PNP
    code gets to them and prevents it from working correctly (Mika
    Westerberg).
 
  - Add a quirk for Lenovo Z50-70 to use the iTCO watchdog instead of
    the WDAT one which conflicts with the RTC on that platform (Mika
    Westerberg).
 
  - Avoid breaking backlight handling on Dell XPS 13 2013 model by
    allowing laptops to use the ACPI backlight by default even if they
    are Windows 8-ready in principle (Hans de Goede).
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Merge tag 'acpi-4.17-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull ACPI fixes from Rafael Wysocki:
 "These are two watchdog-related fixes, fix for a backlight regression
  from the 4.16 cycle that unfortunately was propagated to -stable and a
  button module modification to prevent graphics driver modules from
  failing to load due to unmet dependencies if ACPI is disabled from the
  kernel command line.

  Specifics:

   - Change the ACPI subsystem initialization ordering to initialize the
     WDAT watchodg before reserving PNP motherboard resources so as to
     allow the watchdog to allocate its resources before the PNP code
     gets to them and prevents it from working correctly (Mika
     Westerberg).

   - Add a quirk for Lenovo Z50-70 to use the iTCO watchdog instead of
     the WDAT one which conflicts with the RTC on that platform (Mika
     Westerberg).

   - Avoid breaking backlight handling on Dell XPS 13 2013 model by
     allowing laptops to use the ACPI backlight by default even if they
     are Windows 8-ready in principle (Hans de Goede)"

* tag 'acpi-4.17-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  ACPI / video: Only default only_lcd to true on Win8-ready _desktops_
  ACPI / button: make module loadable when booted in non-ACPI mode
  ACPI / watchdog: Prefer iTCO_wdt on Lenovo Z50-70
  ACPI / scan: Initialize watchdog before PNP

drivers/acpi/acpi_video.c

@@ -2123,6 +2123,25 @@ static int __init intel_opregion_present(void)
 	return opregion;
 }
 
+static bool dmi_is_desktop(void)
+{
+	const char *chassis_type;
+
+	chassis_type = dmi_get_system_info(DMI_CHASSIS_TYPE);
+	if (!chassis_type)
+		return false;
+
+	if (!strcmp(chassis_type, "3") || /*  3: Desktop */
+	    !strcmp(chassis_type, "4") || /*  4: Low Profile Desktop */
+	    !strcmp(chassis_type, "5") || /*  5: Pizza Box */
+	    !strcmp(chassis_type, "6") || /*  6: Mini Tower */
+	    !strcmp(chassis_type, "7") || /*  7: Tower */
+	    !strcmp(chassis_type, "11"))  /* 11: Main Server Chassis */
+		return true;
+
+	return false;
+}
+
 int acpi_video_register(void)
 {
 	int ret = 0;
@@ -2143,8 +2162,12 @@ int acpi_video_register(void)
 	 * win8 ready (where we also prefer the native backlight driver, so
 	 * normally the acpi_video code should not register there anyways).
 	 */
-	if (only_lcd == -1)
-		only_lcd = acpi_osi_is_win8();
+	if (only_lcd == -1) {
+		if (dmi_is_desktop() && acpi_osi_is_win8())
+			only_lcd = true;
+		else
+			only_lcd = false;
+	}
 
 	dmi_check_system(video_dmi_table);
 

drivers/acpi/acpi_watchdog.c

@@ -12,23 +12,64 @@
 #define pr_fmt(fmt) "ACPI: watchdog: " fmt
 
 #include <linux/acpi.h>
+#include <linux/dmi.h>
 #include <linux/ioport.h>
 #include <linux/platform_device.h>
 
 #include "internal.h"
 
+static const struct dmi_system_id acpi_watchdog_skip[] = {
+	{
+		/*
+		 * On Lenovo Z50-70 there are two issues with the WDAT
+		 * table. First some of the instructions use RTC SRAM
+		 * to store persistent information. This does not work well
+		 * with Linux RTC driver. Second, more important thing is
+		 * that the instructions do not actually reset the system.
+		 *
+		 * On this particular system iTCO_wdt seems to work just
+		 * fine so we prefer that over WDAT for now.
+		 *
+		 * See also https://bugzilla.kernel.org/show_bug.cgi?id=199033.
+		 */
+		.ident = "Lenovo Z50-70",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "20354"),
+			DMI_MATCH(DMI_PRODUCT_VERSION, "Lenovo Z50-70"),
+		},
+	},
+	{}
+};
+
+static const struct acpi_table_wdat *acpi_watchdog_get_wdat(void)
+{
+	const struct acpi_table_wdat *wdat = NULL;
+	acpi_status status;
+
+	if (acpi_disabled)
+		return NULL;
+
+	if (dmi_check_system(acpi_watchdog_skip))
+		return NULL;
+
+	status = acpi_get_table(ACPI_SIG_WDAT, 0,
+				(struct acpi_table_header **)&wdat);
+	if (ACPI_FAILURE(status)) {
+		/* It is fine if there is no WDAT */
+		return NULL;
+	}
+
+	return wdat;
+}
+
 /**
  * Returns true if this system should prefer ACPI based watchdog instead of
  * the native one (which are typically the same hardware).
  */
 bool acpi_has_watchdog(void)
 {
-	struct acpi_table_header hdr;
-
-	if (acpi_disabled)
-		return false;
-
-	return ACPI_SUCCESS(acpi_get_table_header(ACPI_SIG_WDAT, 0, &hdr));
+	return !!acpi_watchdog_get_wdat();
 }
 EXPORT_SYMBOL_GPL(acpi_has_watchdog);
 
@@ -41,12 +82,10 @@ void __init acpi_watchdog_init(void)
 	struct platform_device *pdev;
 	struct resource *resources;
 	size_t nresources = 0;
-	acpi_status status;
 	int i;
 
-	status = acpi_get_table(ACPI_SIG_WDAT, 0,
-				(struct acpi_table_header **)&wdat);
-	if (ACPI_FAILURE(status)) {
+	wdat = acpi_watchdog_get_wdat();
+	if (!wdat) {
 		/* It is fine if there is no WDAT */
 		return;
 	}

drivers/acpi/button.c

@@ -635,4 +635,26 @@ module_param_call(lid_init_state,
 		  NULL, 0644);
 MODULE_PARM_DESC(lid_init_state, "Behavior for reporting LID initial state");
 
-module_acpi_driver(acpi_button_driver);
+static int acpi_button_register_driver(struct acpi_driver *driver)
+{
+	/*
+	 * Modules such as nouveau.ko and i915.ko have a link time dependency
+	 * on acpi_lid_open(), and would therefore not be loadable on ACPI
+	 * capable kernels booted in non-ACPI mode if the return value of
+	 * acpi_bus_register_driver() is returned from here with ACPI disabled
+	 * when this driver is built as a module.
+	 */
+	if (acpi_disabled)
+		return 0;
+
+	return acpi_bus_register_driver(driver);
+}
+
+static void acpi_button_unregister_driver(struct acpi_driver *driver)
+{
+	if (!acpi_disabled)
+		acpi_bus_unregister_driver(driver);
+}
+
+module_driver(acpi_button_driver, acpi_button_register_driver,
+	       acpi_button_unregister_driver);

drivers/acpi/scan.c

@@ -2166,10 +2166,10 @@ int __init acpi_scan_init(void)
 	acpi_cmos_rtc_init();
 	acpi_container_init();
 	acpi_memory_hotplug_init();
+	acpi_watchdog_init();
 	acpi_pnp_init();
 	acpi_int340x_thermal_init();
 	acpi_amba_init();
-	acpi_watchdog_init();
 	acpi_init_lpit();
 
 	acpi_scan_add_handler(&generic_device_handler);