[PATCH] x86: add ASRock Q1900DC-ITX mainboard reboot quirk

[Stefan Lippers-Hollmann]

The ASRock Q1900DC-ITX mainboard (Baytrail-D) hangs randomly in both
BIOS and UEFI mode while rebooting unless reboot=pci is used. Add a
quirk to reboot via the pci method.

Signed-off-by: Stefan Lippers-Hollmann <s.l-h@xxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---

The problem is very intermittent and hard to debug, it might succeed
rebooting just fine 40 times in a row - but fails half a dozen times
the next day. It seems to be slightly less common in BIOS CSM mode
than native UEFI (with the CSM disabled), but it does happen in either
mode. Since I've started testing this patch in late january, rebooting
has been 100% reliable.

Most of the time it already hangs during POST, but occassionally it
might even make it through the bootloader and the kernel might even
start booting, but then hangs before the mode switch. The same symptoms
occur with grub-efi, gummiboot and grub-pc, just as well as (at least)
kernel 3.16-3.19 and 4.0-rc6 (I haven't tried older kernels than 3.16). 
Upgrading to the most current mainboard firmware of the ASRock 
Q1900DC-ITX, version 1.20, does not improve the situation.

Searching the web seems to suggest that other Bay Trail-D mainboards
might be affected as well.

The patch applies without problems against 3.19, 4.0-rc and linux-next.

 arch/x86/kernel/reboot.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -183,6 +183,16 @@ static struct dmi_system_id __initdata r
 		},
 	},
 
+	/* ASRock */
+	{	/* Handle problems with rebooting on ASRock Q1900DC-ITX */
+		.callback = set_pci_reboot,
+		.ident = "ASRock Q1900DC-ITX",
+		.matches = {
+			DMI_MATCH(DMI_BOARD_VENDOR, "ASRock"),
+			DMI_MATCH(DMI_BOARD_NAME, "Q1900DC-ITX"),
+		},
+	},
+
 	/* ASUS */
 	{	/* Handle problems with rebooting on ASUS P4S800 */
 		.callback = set_bios_reboot,
-- 
2.1.4

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