gnss: add GNSS assistance support

Automatically fetch the GNSS assistance data from the Web
to heavily reduce the time to acquire a GNSS lock by uploading
the assistance data to the modem.
This feature is optional and can be disabled in the configuration
as people may prefer to not download the assistance data from
the Quectel/Qualcomm servers.
Also configure the GNSS engine to optimize the performance
and power consumption.

data/pine64,pinephone-1.2.toml

@@ -37,13 +37,33 @@ configure = [
     { cmd = "QCFG", subcmd = "ims", expect = "1" },
     { cmd = "QCFG", subcmd = "apready", expect = "1,0,500" },
     { cmd = "QURCCFG", subcmd = "urcport", expect = "\"all\"" },
-    { cmd = "QGPS", value = "1" },
     { cmd = "QSCLK", value = "1" },
+# GNSS configuration:
+#   * Enable A-GPS data upload support (XTRA)
+#   * Disable On-Demand-Positioning (ODP) mode 
+#     to avoid running the GNSS system in the background, even when not enabled.
+#   * Enable Dynamic Power Optimizations (DPO) mode to turn off GNSS RF radios 
+#     when they are not in use.
+#   * Only enable GPS and GLONASS, disable other GNSS systems.
+#     A-GPS data upload doesn't work for Galileo anyway.
+#   * Avoid turning on GNSS support automatically when the modem boots.
+    { cmd = "QGPSXTRA", expect = "1" },
+    { cmd = "QGPSCFG", subcmd = "gnssconfig", expect = "4" },
+    { cmd = "QGPSCFG", subcmd = "odpcontrol", expect = "0" },
+    { cmd = "QGPSCFG", subcmd = "dpoenable", expect = "1" },
+    { cmd = "QGPSCFG", subcmd = "gpsnmeatype", expect = "31" },
+    { cmd = "QGPSCFG", subcmd = "glonassnmeatype", expect = "7" },
+    { cmd = "QGPSCFG", subcmd = "galileonmeatype", expect = "0" },
+    { cmd = "QGPSCFG", subcmd = "beidounmeatype", expect = "0" },
+    { cmd = "QGPSCFG", subcmd = "autogps", expect = "0" },
 ]
 suspend = [
-    { cmd = "QGPSEND" },
 ]
 resume = [
-    { cmd = "QGPS", value = "1" }
 ]
 reset = [ { cmd = "CFUN", value = "1,1" } ]
+
+[gnss]
+enabled = true
+url = "https://xtrapath4.izatcloud.net"
+file = "xtra2.bin"