mb/google/octopus/variants/bobba: Disable XHCI LFPS power management

LTE module is lost after idle overnight, with this workaround,
host will not initiate U3 wakeup at the same time with device,
which will avoid the race condition.

Disable XHCI LFPS power management.
If the option is set in the devicetree, the bits[7:4] in
XHCI MMIO BAR + offset 0x80A4 (PMCTRL_REG) will be updated
from default 9 to 0.

BUG=b:146768983
BRANCH=octopus
TEST=build coreboot with DisableXhciLfpsPM being set to 1 and flash
     the image to the device. Run following command to check if
     bits[7:4] is set 0:
     >iotools mmio_read32 "XHCI MMIO BAR + 0x80A4"

Signed-off-by: Pan Sheng-Liang <sheng-liang.pan@quanta.corp-partner.google.com>
Change-Id: Ib8e5ae79e097debf0c75ead232ddbb2baced2a2a
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40303
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marco Chen <marcochen@google.com>
Reviewed-by: Henry Sun <henrysun@google.com>
Reviewed-by: Justin TerAvest <teravest@chromium.org>

src/mainboard/google/octopus/variants/bobba/overridetree.cb

@@ -214,4 +214,5 @@ chip soc/intel/apollolake
 
 	# Disable compliance mode
 	register "DisableComplianceMode" = "1"
+	register "disable_xhci_lfps_pm" = "0"
 end

src/mainboard/google/octopus/variants/bobba/variant.c

@@ -8,6 +8,7 @@
 #include <delay.h>
 #include <gpio.h>
 #include <ec/google/chromeec/ec.h>
+#include <soc/intel/apollolake/chip.h>
 
 enum {
 	SKU_37_DROID = 37, /* LTE */
@@ -74,3 +75,24 @@ void variant_smi_sleep(u8 slp_typ)
 		return;
 	}
 }
+
+
+void variant_update_devtree(struct device *dev)
+{
+	struct soc_intel_apollolake_config *cfg = NULL;
+
+	cfg = (struct soc_intel_apollolake_config *)dev->chip_info;
+
+	if (cfg != NULL && cfg->disable_xhci_lfps_pm) {
+		switch (google_chromeec_get_board_sku()) {
+		case 37:
+		case 38:
+		case 39:
+		case 40:
+			cfg->disable_xhci_lfps_pm = 1;
+			return;
+		default:
+			return;
+		}
+	}
+}