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Commit 18d78b64 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

ACPI / init: Make it possible to override _REV 



The platform firmware on some systems expects Linux to return "5" as
the supported ACPI revision which makes it expose system configuration
information in a special way.

For example, based on what ACPI exports as the supported revision,
Dell XPS 13 (2015) configures its audio device to either work in HDA
mode or in I2S mode, where the former is supposed to be used on Linux
until the latter is fully supported (in the kernel as well as in user
space).

Since ACPI 6 mandates that _REV should return "2" if ACPI 2 or later
is supported by the OS, a subsequent change will make that happen, so
make it possible to override that on systems where "5" is expected to
be returned for Linux to work correctly one them (such as the Dell
machine mentioned above).

Original-by: default avatarDominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent ce55d01e

Documentation/kernel-parameters.txt

+6 −0
Original line number Diff line number Diff line
@@ -274,6 +274,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
	acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS

			Format: To spoof as Windows 98: ="Microsoft Windows"



	acpi_rev_override [ACPI] Override the _REV object to return 5 (instead

			of 2 which is mandated by ACPI 6) as the supported ACPI

			specification revision (when using this switch, it may

			be necessary to carry out a cold reboot _twice_ in a

			row to make it take effect on the platform firmware).



	acpi_osi=	[HW,ACPI] Modify list of supported OS interface strings

			acpi_osi="string1"	# add string1

			acpi_osi="!string2"	# remove string2

drivers/acpi/Kconfig

+20 −0
Original line number Diff line number Diff line
@@ -77,6 +77,26 @@ config ACPI_PROCFS_POWER 


	  Say N to delete power /proc/acpi/ directories that have moved to /sys/



config ACPI_REV_OVERRIDE_POSSIBLE

	bool "Allow supported ACPI revision to be overriden"

	depends on X86

	default y

	help

	  The platform firmware on some systems expects Linux to return "5" as

	  the supported ACPI revision which makes it expose system configuration

	  information in a special way.



	  For example, based on what ACPI exports as the supported revision,

	  Dell XPS 13 (2015) configures its audio device to either work in HDA

	  mode or in I2S mode, where the former is supposed to be used on Linux

	  until the latter is fully supported (in the kernel as well as in user

	  space).



	  This option enables a DMI-based quirk for the above Dell machine (so

	  that HDA audio is exposed by the platform firmware to the kernel) and

	  makes it possible to force the kernel to return "5" as the supported

	  ACPI revision via the "acpi_rev_override" command line switch.



config ACPI_EC_DEBUGFS

	tristate "EC read/write access through /sys/kernel/debug/ec"

	default n

drivers/acpi/blacklist.c

+26 −0
Original line number Diff line number Diff line
@@ -162,6 +162,15 @@ static int __init dmi_disable_osi_win8(const struct dmi_system_id *d) 
	acpi_osi_setup("!Windows 2012");

	return 0;

}

#ifdef CONFIG_ACPI_REV_OVERRIDE_POSSIBLE

static int __init dmi_enable_rev_override(const struct dmi_system_id *d)

{

	printk(KERN_NOTICE PREFIX "DMI detected: %s (force ACPI _REV to 5)\n",

	       d->ident);

	acpi_rev_override_setup(NULL);

	return 0;

}

#endif



static struct dmi_system_id acpi_osi_dmi_table[] __initdata = {

	{
@@ -325,6 +334,23 @@ static struct dmi_system_id acpi_osi_dmi_table[] __initdata = { 
		     DMI_MATCH(DMI_PRODUCT_NAME, "1015PX"),

		},

	},



#ifdef CONFIG_ACPI_REV_OVERRIDE_POSSIBLE

	/*

	 * DELL XPS 13 (2015) switches sound between HDA and I2S

	 * depending on the ACPI _REV callback. If userspace supports

	 * I2S sufficiently (or if you do not care about sound), you

	 * can safely disable this quirk.

	 */

	{

	 .callback = dmi_enable_rev_override,

	 .ident = "DELL XPS 13 (2015)",

	 .matches = {

		      DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),

		      DMI_MATCH(DMI_PRODUCT_NAME, "XPS 13 9343"),

		},

	},

#endif

	{}

};

drivers/acpi/internal.h

+1 −0
Original line number Diff line number Diff line
@@ -58,6 +58,7 @@ void acpi_cmos_rtc_init(void); 
#else

static inline void acpi_cmos_rtc_init(void) {}

#endif

int acpi_rev_override_setup(char *str);



extern bool acpi_force_hot_remove;

drivers/acpi/osl.c

+18 −0
Original line number Diff line number Diff line
@@ -537,6 +537,19 @@ acpi_os_get_physical_address(void *virt, acpi_physical_address * phys) 
}

#endif



#ifdef CONFIG_ACPI_REV_OVERRIDE_POSSIBLE

static bool acpi_rev_override;



int __init acpi_rev_override_setup(char *str)

{

	acpi_rev_override = true;

	return 1;

}

__setup("acpi_rev_override", acpi_rev_override_setup);

#else

#define acpi_rev_override	false

#endif



#define ACPI_MAX_OVERRIDE_LEN 100



static char acpi_os_name[ACPI_MAX_OVERRIDE_LEN];
@@ -555,6 +568,11 @@ acpi_os_predefined_override(const struct acpi_predefined_names *init_val, 
		*new_val = acpi_os_name;

	}



	if (!memcmp(init_val->name, "_REV", 4) && acpi_rev_override) {

		printk(KERN_INFO PREFIX "Overriding _REV return value to 5\n");

		*new_val = (char *)5;

	}



	return AE_OK;

}