slippy: Enable EC SMI

Enable GPIO SMI for GPIO34 and set it as inverted so it
is only generated when it is raised by the EC.

1) ec console command: lidopen
2) wait until booted to developer screen
3) ec console command: lidclose
4) ensure system turns off

Change-Id: I7d50f171f3f4539c7c264103d1ffc7c5d0f1c7ba
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/56052
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/4177
Tested-by: build bot (Jenkins)
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>

src/mainboard/google/slippy/devicetree.cb

@@ -57,7 +57,8 @@ chip northbridge/intel/haswell
 			register "gen1_dec" = "0x00fc0801"
 			register "gen2_dec" = "0x00fc0901"
 
-			register "alt_gp_smi_en" = "0x0000"
+			# EC_SMI is GPIO34
+			register "alt_gp_smi_en" = "0x0004"
 			register "gpe0_en_1" = "0x00000000"
 			# EC_SCI is GPIO36
 			register "gpe0_en_2" = "0x00000010"

src/southbridge/intel/lynxpoint/lp_gpio.h

@@ -110,7 +110,7 @@
 	  .route = GPIO_ROUTE_SCI }
 
 #define LP_GPIO_ACPI_SMI \
-	{ .conf0 = GPIO_MODE_GPIO | GPIO_DIR_INPUT, \
+	{ .conf0 = GPIO_MODE_GPIO | GPIO_DIR_INPUT | GPIO_INVERT, \
 	  .owner = GPIO_OWNER_ACPI, \
 	  .route = GPIO_ROUTE_SMI }