intel/apollolake: Set sleep type to S5 on vboot reboot request

Add support for vboot_platform_prepare_reboot which is called whenever
vboot requests reboot of the platform. SLP_TYPE needs to be set to S5 in
such conditions since the platform would no longer be in a resuming
state after reset.

Change-Id: I01392bfda90c9274cd52c1004555d250b1d539b7
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/15340
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/apollolake/pmutil.c

@@ -399,3 +399,16 @@ void global_reset_enable(bool enable)
 	reg = enable ? reg | CF9_GLB_RST : reg & ~CF9_GLB_RST;
 	write32((void *)etr, reg);
 }
+
+/*
+ * The PM1 control is set to S5 when vboot requests a reboot because the power
+ * state code above may not have collected its data yet. Therefore, set it to
+ * S5 when vboot requests a reboot. That's necessary if vboot fails in the
+ * resume path and requests a reboot. This prevents a reboot loop where the
+ * error is continually hit on the failing vboot resume path.
+ */
+void vboot_platform_prepare_reboot(void)
+{
+	const uint16_t port = ACPI_PMIO_BASE + PM1_CNT;
+	outl((inl(port) & ~(SLP_TYP)) | (SLP_TYP_S5 << SLP_TYP_SHIFT), port);
+}