intel/skylake: disable ACPI PM Timer to enable XTAL OSC shutdown

Keeping ACPI PM timer alive prevents XTAL OSC shutdown in S0ix
which has a power impact.

Based on a DT variable, this patch disables the ACPI PM timer
late in the boot sequence - disabling earlier will lead to a hang
since the FSP boot flow needs this timer. This also hides the ACPI PM
timer from the OS by removing from FADT table. Once the ACPI PM timer
is disabled, TCO gets switched off as well.

BRANCH=none
BUG=chrome-os-partner:48646
TEST=Build for skylake board with the PmTimerDisabled policy in
devicetree set to 1.
iotools mmio_read32 0xfe0000fc should return 0x2.
cat /sys/devices/system/clocksource/clocksource0/available_clocksource
should list only "tsc hpet". acpi_pm should be removed from this list.

Change-Id: Icfdc51bc33b5190a55196d67e18afdaaa2f9b310
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 18bcb8a434b029295e1f1cc925e2b47e79254583
Original-Change-Id: Ifebe8bb5a7978339e07e4e12e174b9b978135467
Original-Signed-off-by: Archana Patni <archana.patni@intel.com>
Original-Signed-off-by: Subramony Sesha <subramony.sesha@intel.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/319361
Original-Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/13588
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

3 files changed, 32 insertions, 8 deletions

diff --git a/src/soc/intel/skylake/acpi.c b/src/soc/intel/skylake/acpi.c
index c01066f7fb..678e0a9f3f 100644
--- a/src/soc/intel/skylake/acpi.c
+++ b/src/soc/intel/skylake/acpi.c
@@ -217,6 +217,8 @@ unsigned long acpi_fill_madt(unsigned long current)
 void acpi_fill_in_fadt(acpi_fadt_t *fadt)
 {
 	const uint16_t pmbase = ACPI_BASE_ADDRESS;
+	const struct device *dev = dev_find_slot(0, PCH_DEVFN_LPC);
+	config_t *config = dev->chip_info;
 
 	fadt->sci_int = acpi_sci_irq();
 	fadt->smi_cmd = APM_CNT;
@@ -230,14 +232,16 @@ void acpi_fill_in_fadt(acpi_fadt_t *fadt)
 	fadt->pm1a_cnt_blk = pmbase + PM1_CNT;
 	fadt->pm1b_cnt_blk = 0x0;
 	fadt->pm2_cnt_blk = pmbase + PM2_CNT;
-	fadt->pm_tmr_blk = pmbase + PM1_TMR;
+	if (config->PmTimerDisabled == 0)
+		fadt->pm_tmr_blk = pmbase + PM1_TMR;
 	fadt->gpe0_blk = pmbase + GPE0_STS(0);
 	fadt->gpe1_blk = 0;
 
 	fadt->pm1_evt_len = 4;
 	fadt->pm1_cnt_len = 2;
 	fadt->pm2_cnt_len = 1;
-	fadt->pm_tmr_len = 4;
+	if (config->PmTimerDisabled == 0)
+		fadt->pm_tmr_len = 4;
 	/* There are 4 GPE0 STS/EN pairs each 32 bits wide. */
 	fadt->gpe0_blk_len = 2 * GPE0_REG_MAX * sizeof(uint32_t);
 	fadt->gpe1_blk_len = 0;
@@ -302,12 +306,14 @@ void acpi_fill_in_fadt(acpi_fadt_t *fadt)
 	fadt->x_pm2_cnt_blk.addrl = pmbase + PM2_CNT;
 	fadt->x_pm2_cnt_blk.addrh = 0x0;
 
-	fadt->x_pm_tmr_blk.space_id = 1;
-	fadt->x_pm_tmr_blk.bit_width = fadt->pm_tmr_len * 8;
-	fadt->x_pm_tmr_blk.bit_offset = 0;
-	fadt->x_pm_tmr_blk.resv = 0;
-	fadt->x_pm_tmr_blk.addrl = pmbase + PM1_TMR;
-	fadt->x_pm_tmr_blk.addrh = 0x0;
+	if (config->PmTimerDisabled == 0) {
+		fadt->x_pm_tmr_blk.space_id = 1;
+		fadt->x_pm_tmr_blk.bit_width = fadt->pm_tmr_len * 8;
+		fadt->x_pm_tmr_blk.bit_offset = 0;
+		fadt->x_pm_tmr_blk.resv = 0;
+		fadt->x_pm_tmr_blk.addrl = pmbase + PM1_TMR;
+		fadt->x_pm_tmr_blk.addrh = 0x0;
+	}
 
 	fadt->x_gpe0_blk.space_id = 0;
 	fadt->x_gpe0_blk.bit_width = 0;
diff --git a/src/soc/intel/skylake/chip.h b/src/soc/intel/skylake/chip.h
index 0390edaaea..0b87f2d08e 100644
--- a/src/soc/intel/skylake/chip.h
+++ b/src/soc/intel/skylake/chip.h
@@ -325,6 +325,7 @@ struct soc_intel_skylake_config {
 	u8 HeciEnabled;
 	/* PL2 Override value in Watts */
 	u32 tdp_pl2_override;
+	u8 PmTimerDisabled;
 };
 
 typedef struct soc_intel_skylake_config config_t;
diff --git a/src/soc/intel/skylake/finalize.c b/src/soc/intel/skylake/finalize.c
index 13df7ccdaf..5eef66dbbb 100644
--- a/src/soc/intel/skylake/finalize.c
+++ b/src/soc/intel/skylake/finalize.c
@@ -38,6 +38,7 @@
 #define PCH_P2SB_EPMASK(mask_number) 	PCH_P2SB_EPMASK0 + (mask_number * 4)
 
 #define PCH_P2SB_E0			0xE0
+#define PCH_PWRM_ACPI_TMR_CTL		0xFC
 
 static void pch_configure_endpoints(device_t dev, int epmask_id, uint32_t mask)
 {
@@ -92,6 +93,7 @@ static void pch_finalize_script(void)
 	uint8_t *pmcbase;
 	config_t *config;
 	u32 pmsyncreg;
+	u8 reg8;
 
 	/* Set SPI opcode menu */
 	write16(spibar + SPIBAR_PREOP, SPI_OPPREFIX);
@@ -126,6 +128,21 @@ static void pch_finalize_script(void)
 
 	/* we should disable Heci1 based on the devicetree policy */
 	config = dev->chip_info;
+
+	/*
+	 * Disable ACPI PM timer based on dt policy
+	 *
+	 * Disabling ACPI PM timer is necessary for XTAL OSC shutdown.
+	 * Disabling ACPI PM timer also switches off TCO
+	 */
+
+	if (config->PmTimerDisabled) {
+		reg8 = read8(pmcbase + PCH_PWRM_ACPI_TMR_CTL);
+		reg8 |= (1 << 1);
+		write8(pmcbase + PCH_PWRM_ACPI_TMR_CTL, reg8);
+	}
+
+	/* we should disable Heci1 based on the devicetree policy */
 	if (config->HeciEnabled == 0)
 		pch_disable_heci();
 }