soc/intel/skylake: Implement GPIO ACPI AML generating functions

Implement GPIO ACPI AML generating functions that can be called by
coreboot drivers to generate GPIO manipulation code in AML. Following
API functions are implemented:

1. acpigen_soc_read_rx_gpio
2. acpigen_soc_get_tx_gpio
3. acpigen_soc_set_tx_gpio
4. acpigen_soc_clear_tx_gpio

In addition to the API functions above, helper functions are added to
gpio.asl to set/clear/get Tx value of GPIO.

BUG=b:62028489

Change-Id: I77e5d0decd8929a922d06b02312378f092551667
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/19828
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 37 insertions, 0 deletions

diff --git a/src/soc/intel/skylake/acpi.c b/src/soc/intel/skylake/acpi.c
index 64438bdd80..77fbb48570 100644
--- a/src/soc/intel/skylake/acpi.c
+++ b/src/soc/intel/skylake/acpi.c
@@ -695,3 +695,40 @@ const char *soc_acpi_name(struct device *dev)
 
 	return NULL;
 }
+
+static int acpigen_soc_gpio_op(const char *op, unsigned int gpio_num)
+{
+	/* op (gpio_num) */
+	acpigen_emit_namestring(op);
+	acpigen_write_integer(gpio_num);
+	return 0;
+}
+
+static int acpigen_soc_get_gpio_state(const char *op, unsigned int gpio_num)
+{
+	/* Store (op (gpio_num), Local0) */
+	acpigen_write_store();
+	acpigen_soc_gpio_op(op, gpio_num);
+	acpigen_emit_byte(LOCAL0_OP);
+	return 0;
+}
+
+int acpigen_soc_read_rx_gpio(unsigned int gpio_num)
+{
+	return acpigen_soc_get_gpio_state("\\_SB.PCI0.GRXS", gpio_num);
+}
+
+int acpigen_soc_get_tx_gpio(unsigned int gpio_num)
+{
+	return acpigen_soc_get_gpio_state("\\_SB.PCI0.GTXS", gpio_num);
+}
+
+int acpigen_soc_set_tx_gpio(unsigned int gpio_num)
+{
+	return acpigen_soc_gpio_op("\\_SB.PCI0.STXS", gpio_num);
+}
+
+int acpigen_soc_clear_tx_gpio(unsigned int gpio_num)
+{
+	return acpigen_soc_gpio_op("\\_SB.PCI0.CTXS", gpio_num);
+}