intel/apollolake: Add power management utility function

This patch adds a power management utility function to
clear wake status bits in ACPI GPE0 registers. We need
to call this function before going to sleep from
common smi handler function.

BUG=chrome-os-partner:55583
BRANCH=None
TEST=Verified that system goes to sleep on lidclose and
     powerd_dbus_suspend command issued from built-in
     keyboard.

Change-Id: Icd095d377c82f2e154f2e2db773f737aa49cda64
Signed-off-by: Shaunak Saha <shaunak.saha@intel.com>
Reviewed-on: https://review.coreboot.org/16298
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/apollolake/include/soc/pm.h

@@ -173,6 +173,7 @@ uint16_t clear_pm1_status(void);
 uint32_t clear_tco_status(void);
 uint32_t clear_gpe_status(void);
 void clear_pmc_status(void);
+void clear_gpi_gpe_sts(void);
 uint32_t get_smi_en(void);
 void enable_smi(uint32_t mask);
 void disable_smi(uint32_t mask);

src/soc/intel/apollolake/pmutil.c

@@ -246,6 +246,16 @@ void disable_all_gpe(void)
 	disable_gpe(~0);
 }
 
+/* Clear the gpio gpe0 status bits in ACPI registers */
+void clear_gpi_gpe_sts(void)
+{
+	int i;
+
+	for (i = 1; i < GPE0_REG_MAX; i++) {
+		uint32_t gpe_sts = inl(ACPI_PMIO_BASE + GPE0_STS(i));
+		outl(gpe_sts, ACPI_PMIO_BASE + GPE0_STS(i));
+	}
+}
 
 static uint32_t reset_gpe_status(void)
 {