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ACPI / OSI: Add OEM _OSI string to enable NVidia HDMI audio 

Some ThinkPad systems have a power-saving feature that turns off HDMI
audio device in Windows, but NVidia Linux driver does not support this
feature. As a result, HDMI audio will not work on Linux.

A BIOS workaround is added with an OEM_OSI string
"Linux-Lenovo-NV-HDMI-Audio" to power on NVidia HDMI audio when booting.

The form of the OEM _OSI strings is defined by each OEMs and is
discussed in Documentation/acpi/osi.txt.

Signed-off-by: Alex Hung <alex.hung@canonical.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Alex Hung 2018-07-18 11:46:55 -07:00 committed by Rafael J. Wysocki
parent 9d3cce1e8b
commit 887532ca7c
1 changed files with 8 additions and 0 deletions
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8
drivers/acpi/osi.c
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@ -66,6 +66,14 @@ osi_setup_entries[OSI_STRING_ENTRIES_MAX] __initdata = {
* be removed if both new and old graphics cards are supported.
*/
{"Linux-Dell-Video", true},
/*
* Linux-Lenovo-NV-HDMI-Audio is used by BIOS to power on NVidia's HDMI
* audio device which is turned off for power-saving in Windows OS.
* This power management feature observed on some Lenovo Thinkpad
* systems which will not be able to output audio via HDMI without
* a BIOS workaround.
*/
{"Linux-Lenovo-NV-HDMI-Audio", true},
};
static u32 acpi_osi_handler(acpi_string interface, u32 supported)