[PATCH 1/1][SRU][Bionic] ACPI / OSI: Add OEM _OSI strings to disable NVidia RTD3

[Alex Hung]

BugLink: https://bugs.launchpad.net/bugs/1773299

A number of Dell systems require an OEM _OSI string "Linux-Dell-Video"
as a BIOS workaround to disable RTD3 which causes systems hangs when
NVidia graphics cards are installed.  The affected Dell systems are
with system IDs: 0818, 0819, 0820, 0850, 0851, 086F, 0870, 0885 and
0886.

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 at canonical.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
(cherry picked from commit 9251a71db62ca9cc7e7cf364218610b0f018c291)
Signed-off-by: Alex Hung <alex.hung at canonical.com>
---
 drivers/acpi/osi.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/acpi/osi.c b/drivers/acpi/osi.c
index c2ef3e6c21ba..081e25e66e1c 100644
--- a/drivers/acpi/osi.c
+++ b/drivers/acpi/osi.c
@@ -57,6 +57,15 @@ osi_setup_entries[OSI_STRING_ENTRIES_MAX] __initdata = {
 	{"Processor Device", true},
 	{"3.0 _SCP Extensions", true},
 	{"Processor Aggregator Device", true},
+	/*
+	 * Linux-Dell-Video is used by BIOS to disable RTD3 for NVidia graphics
+	 * cards as RTD3 is not supported by drivers now.  Systems with NVidia
+	 * cards will hang without RTD3 disabled.
+	 *
+	 * Once NVidia drivers officially support RTD3, this _OSI strings can
+	 * be removed if both new and old graphics cards are supported.
+	 */
+	{"Linux-Dell-Video", true},
 };
 
 static u32 acpi_osi_handler(acpi_string interface, u32 supported)
-- 
2.17.0