soc/intel/common: Disable GPEs just before enabling SMIs

Call to pmc_disable_all_gpe is required before enabling SMIs to ensure
that we do not end up in a recursive SMI handler loop as mentioned in
change 74145f7 (intel/common/pmc: Disable all GPEs during
pmc_init). Thus, this call was added at the end of
pmc_fill_power_state as we want to ensure that all the GPE registers
are backed up before being cleared for identifying the wake source in
ramstage.

This resulted in a side-effect on APL where pmc_fixup_power_state was
called much later in the boot process. Even though we have got rid of
pmc_fixup_power_state, this change moves the call to
pmc_disable_all_gpe to happen just before enabling SMIs. This helps to
keep the disabling of GPEs logically before the enabling of SMIs and
any clean ups that happen in pmc or soc-specific code should not
affect the state of GPEs.

BUG=b:110836465
TEST=Verified that wake sources are correctly identified on KBL and
APL. Also, no SMI handler issues observed when resuming.

Change-Id: I122a8118edcec117f25beee71a23c0a44ae862ed
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/27251
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/common/block/pmc/pmclib.c

@@ -416,18 +416,6 @@ int pmc_fill_power_state(struct chipset_power_state *ps)
 	ps->prev_sleep_state = pmc_prev_sleep_state(ps);
 	printk(BIOS_DEBUG, "prev_sleep_state %d\n", ps->prev_sleep_state);
 
-	/*
-	 * GPEs need to be disabled before enabling SMI. Otherwise, it could
-	 * lead to SMIs being triggered in coreboot preventing the progress of
-	 * normal boot-up. However, GPEs should not be disabled as part of
-	 * pmc_gpe_init which happens in bootblock. Otherwise,
-	 * pmc_fill_power_state would read GPE0_EN registers as all 0s thus
-	 * losing information about the wake source. Hence,
-	 * pmc_disable_all_gpe() is placed here after GPE0_EN registers are
-	 * saved in chipset_power_state.
-	 */
-	pmc_disable_all_gpe();
-
 	return ps->prev_sleep_state;
 }
 

src/soc/intel/common/block/smm/smm.c

@@ -45,6 +45,15 @@ void smm_southbridge_enable(uint16_t pm1_events)
 	pmc_enable_pm1(pm1_events);
 	pmc_disable_std_gpe(PME_B0_EN);
 
+	/*
+	 * GPEs need to be disabled before enabling SMI. Otherwise, it could
+	 * lead to SMIs being triggered in coreboot preventing the progress of
+	 * normal boot-up. This is done as late as possible so that
+	 * pmc_fill_power_state can read the correct state of GPE0_EN* registers
+	 * and not lose information about the wake source.
+	 */
+	pmc_disable_all_gpe();
+
 	/*
 	 * Enable SMI generation:
 	 *  - on APMC writes (io 0xb2)