coreboot: uniformize serial console handling

This commit cleans up the selection of the serial console device and
gives it sensible default values (usually, the DB9 header on the
back I/O panel) on each platform.

src/coreboot/default.nix

@@ -128,7 +128,7 @@ stdenv.mkDerivation {
     echo 'CONFIG_LINUX_INITRD="${initramfs_image}"' >> .config
     sed -i 's/^CONFIG_UART_FOR_CONSOLE=.*//' .config
   '' + lib.optionalString (uart-for-console != null) ''
-    echo 'CONFIG_UART_FOR_CONSOLE=${builtins.toString uart-for-console}"' >> .config
+    echo 'CONFIG_UART_FOR_CONSOLE=${builtins.toString uart-for-console}' >> .config
   '' + lib.optionalString (iasl != null) ''
     echo CONFIG_ANY_TOOLCHAIN=y >> .config
   '' + ''

src/platform/am1i/coreboot.config

@@ -88,17 +88,7 @@ CONFIG_MAINBOARD_DIR="asus/am1i-a"
 CONFIG_MAINBOARD_PART_NUMBER="AM1I-A"
 CONFIG_MAX_CPUS=4
 CONFIG_CBFS_SIZE=8387272
-
-# this is the internal header, which exists on both board variants
-CONFIG_UART_FOR_CONSOLE=0
-CONFIG_TTYS0_BASE=0x3f8
-
-# this is the back-panel connector, which exists only on the "more back-panel stuff" board variant
-#CONFIG_UART_FOR_CONSOLE=1
-#CONFIG_TTYS0_BASE=0x2f8
-
 CONFIG_LINUX_INITRD=""
-
 CONFIG_MAINBOARD_VENDOR="ASUS"
 CONFIG_HW_MEM_HOLE_SIZEK=0x200000
 # CONFIG_HW_MEM_HOLE_SIZE_AUTO_INC is not set

src/platform/am1i/default.nix

@@ -16,7 +16,7 @@
         '';
       });
 
-    console-device = "ttyS0";
+    console-device = "ttyS1";
 
     coreboot = final.lib.makeOverridable (prev.coreboot.override {
       iasl = final.iasl_20180531;
@@ -24,6 +24,11 @@
       coreboot-toolchain = with final.coreboot-toolchain; [ x64 i386 ];
       fmap = ./custom.fmap;
       config = ./coreboot.config;
+      uart-for-console =
+        if      final.console-device == "ttyS0" then 0 # IDC ribbon-cable header on the motherboarod
+        else if final.console-device == "ttyS1" then 1 # DB9 connector on rear I/O panel; omitted from some board variants
+        else if final.console-device == null then null
+        else throw "am1i currently supports only `null` and `ttyS{0,1}` for `console-device`";
     }).overrideAttrs (a: {
       /*
       postConfigure = (a.postConfigure or "") + ''

src/platform/kevin/coreboot.config

@@ -88,7 +88,6 @@ CONFIG_MAINBOARD_DIR="google/gru"
 CONFIG_MAINBOARD_PART_NUMBER="Kevin"
 CONFIG_MAX_CPUS=1
 CONFIG_CBFS_SIZE=7138520
-CONFIG_UART_FOR_CONSOLE=0
 CONFIG_MAINBOARD_VENDOR="Google"
 CONFIG_DIMM_SPD_SIZE=256
 CONFIG_DEVICETREE="devicetree.cb"

src/platform/kevin/default.nix

@@ -79,6 +79,10 @@ in {
         fmap = ./custom.fmap;
         config = ./coreboot.config;
         coreboot-toolchain = with final.coreboot-toolchain; [ aarch64 ];
+        uart-for-console =
+          if final.console-device == "ttyS2" then 0
+          else if final.console-device == null then null
+          else throw "gru-kevin currently supports only `null` and `ttyS2` for `console-device`";
       }).overrideAttrs (a: {
         postConfigure = ''
           echo CONFIG_ARM64_BL31_EXTERNAL_FILE=\"${atf}/bl31.elf\" >> .config

src/platform/kgpe/coreboot.config

@@ -89,8 +89,6 @@ CONFIG_MAINBOARD_DIR="asus/kgpe-d16"
 CONFIG_MAINBOARD_PART_NUMBER="KGPE-D16"
 CONFIG_MAX_CPUS=32
 CONFIG_CBFS_SIZE=8387584
-#CONFIG_UART_FOR_CONSOLE=0
-CONFIG_UART_FOR_CONSOLE=1
 CONFIG_MAINBOARD_VENDOR="ASUS"
 CONFIG_APIC_ID_OFFSET=0x0
 CONFIG_HW_MEM_HOLE_SIZEK=0x100000
@@ -193,7 +191,6 @@ CONFIG_PCIEXP_CLK_PM=y
 CONFIG_BOOTBLOCK_NORTHBRIDGE_INIT="northbridge/amd/amdfam10/bootblock.c"
 CONFIG_BOOTBLOCK_SOUTHBRIDGE_INIT="southbridge/amd/sb700/bootblock.c"
 CONFIG_TTYS0_BASE=0x3f8
-#CONFIG_TTYS0_BASE=0x2f8
 CONFIG_RAMTOP=0x400000
 # CONFIG_CONSOLE_CBMEM is not set
 CONFIG_UART_PCI_ADDR=0x0

src/platform/kgpe/default.nix

@@ -31,6 +31,8 @@
     # insecure configurations? (63xx without microcode)
     microcode-blob = null;
 
+    console-device = "ttyS0";   # the DB9 connector on the rear panel
+
     # This contains the default values written into the
     # battery-backed nvram when you boot with the recovery jumper
     # installed (which is something you should do the first time you
@@ -41,15 +43,17 @@
     # TODO: use a NixOS-style structuredConfig for this.
     cmos-default = null;
 
-    console-device = "ttyS0";   # the DB9 connector on the rear panel
-    #console-device = "ttyS1";  # the IDC header on the motherboard
-
     coreboot = final.lib.makeOverridable (prev.coreboot.override {
       iasl = final.iasl_20180531;
       payload = "${final.kernel}/bzImage";
       fmap = ./custom.fmap;
       config = ./coreboot.config;
       coreboot-toolchain = with final.coreboot-toolchain; [ x64 i386 ];
+      uart-for-console =
+        if      final.console-device == "ttyS0" then 0 # the DB9 connector on the rear panel
+        else if final.console-device == "ttyS1" then 1 # the IDC header on the motherboard
+        else if final.console-device == null then null
+        else throw "kgpe currently supports only `null` and `ttyS{0,1}` for `console-device`";
     }).overrideAttrs (a: {
       postConfigure = if final.microcode-blob != null then ''
         echo CONFIG_CPU_MICROCODE_MULTIPLE_FILES=y >> .config