3 files changed, 25 insertions, 0 deletions

diff --git a/src/soc/intel/apollolake/Kconfig b/src/soc/intel/apollolake/Kconfig
index b7f2dc92c4..a9f49dbbfd 100644
--- a/src/soc/intel/apollolake/Kconfig
+++ b/src/soc/intel/apollolake/Kconfig
@@ -57,6 +57,7 @@ config CPU_SPECIFIC_OPTIONS
 	select PCIEX_LENGTH_256MB
 	select POSTCAR_CONSOLE
 	select POSTCAR_STAGE
+	select PMC_INVALID_READ_AFTER_WRITE
 	select REG_SCRIPT
 	select RELOCATABLE_RAMSTAGE	# Build fails if this is not selected
 	select RTC
diff --git a/src/soc/intel/common/block/pmc/Kconfig b/src/soc/intel/common/block/pmc/Kconfig
index cfd12d8f3e..46f134e3b1 100644
--- a/src/soc/intel/common/block/pmc/Kconfig
+++ b/src/soc/intel/common/block/pmc/Kconfig
@@ -30,3 +30,10 @@ config POWER_STATE_PREVIOUS_AFTER_FAILURE
 	  power
 
 endchoice
+
+config PMC_INVALID_READ_AFTER_WRITE
+	bool
+	default n
+	help
+	  Enable this for PMC devices where a read back of ACPI BAR and
+	  IO access bit does not return the previously written value.
diff --git a/src/soc/intel/common/block/pmc/pmc.c b/src/soc/intel/common/block/pmc/pmc.c
index a3c5c4216c..f9563302df 100644
--- a/src/soc/intel/common/block/pmc/pmc.c
+++ b/src/soc/intel/common/block/pmc/pmc.c
@@ -65,6 +65,23 @@ static void pch_pmc_add_io_resources(struct device *dev,
 			cfg->abase_addr, cfg->abase_size,
 			 IORESOURCE_IO | IORESOURCE_ASSIGNED |
 			 IORESOURCE_FIXED);
+	if (IS_ENABLED(CONFIG_PMC_INVALID_READ_AFTER_WRITE)) {
+		/*
+		 * The ACPI IO BAR (offset 0x20) is not PCI compliant. We've
+		 * observed cases where the BAR reads back as 0, but the IO
+		 * window is open. This also means that it will not respond
+		 * to PCI probing.
+		 */
+		pci_write_config16(dev, cfg->abase_offset, cfg->abase_addr);
+		/*
+		 * In pci_dev_enable_resources, reading IO SPACE ACCESS bit in
+		 * STATUSCOMMAND register does not read back the written
+		 * value correctly, hence IO access gets disabled. This is
+		 * seen in some PMC devices, hence this code makes sure
+		 * IO access is available.
+		 */
+		dev->command |= PCI_COMMAND_IO;
+	}
 }
 
 static void pch_pmc_read_resources(struct device *dev)