2 files changed, 109 insertions, 0 deletions

diff --git a/src/soc/amd/common/block/graphics/Kconfig b/src/soc/amd/common/block/graphics/Kconfig
index 8aa2a20a3c..4cda353c5f 100644
--- a/src/soc/amd/common/block/graphics/Kconfig
+++ b/src/soc/amd/common/block/graphics/Kconfig
@@ -3,3 +3,11 @@ config SOC_AMD_COMMON_BLOCK_GRAPHICS
 	default n
 	help
 	  Select this option to use AMD common graphics driver support.
+
+config SOC_AMD_COMMON_BLOCK_GRAPHICS_ATIF
+	bool
+	depends on SOC_AMD_COMMON_BLOCK_GRAPHICS
+	help
+	  Select this option to provide ATIF method with display brightness querying.
+	  Currently, the exported values only open up 0-255 as the brightness range for
+	  the display.
diff --git a/src/soc/amd/common/block/graphics/graphics.c b/src/soc/amd/common/block/graphics/graphics.c
index 466a91c666..24cabfe454 100644
--- a/src/soc/amd/common/block/graphics/graphics.c
+++ b/src/soc/amd/common/block/graphics/graphics.c
@@ -1,13 +1,114 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later */
 
 #include <acpi/acpi_device.h>
+#include <acpi/acpigen.h>
 #include <device/pci.h>
 #include <device/pci_ids.h>
 
+#define ATIF_FUNCTION_VERIFY_INTERFACE 0x0
+struct atif_verify_interface_output {
+	uint16_t size; /* Size of this object, including size field */
+	uint16_t version;
+	uint32_t supported_notifications;
+	uint32_t supported_functions; /* Bit n set if function n+1 supported. */
+};
+
+#define ATIF_FUNCTION_QUERY_BRIGHTNESS_TRANSFER_CHARACTERISTICS    0x10
+# define ATIF_QBTC_REQUEST_LCD1                              0
+/* error codes */
+# define ATIF_QBTC_ERROR_CODE_SUCCESS                        0
+# define ATIF_QBTC_ERROR_CODE_FAILURE                        1
+# define ATIF_QBTC_ERROR_CODE_DEVICE_NOT_SUPPORTED           2
+struct atif_brightness_input {
+	uint16_t size;
+	/* ATIF doc indicates this field is a word, but the kernel drivers uses a byte. */
+	uint8_t requested_display;
+};
+struct atif_brightness_output {
+	uint16_t size; /* Size of this object, including size field. */
+	uint16_t flags; /* Currently all reserved. */
+	uint8_t error_code;
+	/* default brightness fields currently ignored by Linux driver. */
+	uint8_t default_brightness_ac; /* Percentage brightness when connected to AC. */
+	uint8_t default_brightness_dc; /* Percentage brightness when connected to DC. */
+	/* The following 2 fields are the only ones honored by Linux driver currently. */
+	uint8_t min_input_signal_level; /* 0-255 corresponding to 0% */
+	uint8_t max_input_signal_level; /* 0-255 corresponding to 100% */
+	/* Array of data points consisting of:
+	 *  { uint8_t luminance_level; (percent)
+	 *    uint8_t input_signal_level; (0-255 in value) }
+	 * Linux ignores these fields so no support currently. */
+	uint8_t count_data_points; /* Count of data points. */
+};
+
+static void generate_atif(const struct device *dev)
+{
+	struct atif_verify_interface_output verify_output = {
+		.size = sizeof(verify_output),
+		.version = 1,
+		.supported_functions =
+			BIT(ATIF_FUNCTION_QUERY_BRIGHTNESS_TRANSFER_CHARACTERISTICS - 1),
+	};
+	struct atif_brightness_output brightness_error = {
+		.size = sizeof(brightness_error),
+		.error_code = ATIF_QBTC_ERROR_CODE_DEVICE_NOT_SUPPORTED,
+	};
+	struct atif_brightness_output brightness_out = {
+		.size = sizeof(brightness_out),
+		.error_code = ATIF_QBTC_ERROR_CODE_SUCCESS,
+		.min_input_signal_level = 0,
+		.max_input_signal_level = 255,
+	};
+
+	/* Scope (\_SB.PCI0.PBRA.IGFX) */
+	acpigen_write_scope(acpi_device_path(dev));
+	/* Method (ATIF, 2, NotSerialized) */
+	acpigen_write_method("ATIF", 2);
+	/* ToInteger (Arg0, Local0) */
+	acpigen_write_to_integer(ARG0_OP, LOCAL0_OP);
+
+	/* If ((Local0 == Zero)) */
+	acpigen_write_if_lequal_op_int(LOCAL0_OP, ATIF_FUNCTION_VERIFY_INTERFACE);
+	/* Return (Buffer (0x0C) { ... } */
+	acpigen_write_return_byte_buffer((uint8_t *)(void *)&verify_output,
+		sizeof(verify_output));
+	acpigen_pop_len(); /* if (LEqual(Local0, 0) */
+
+	/* ElseIf ((Local0 == 0x10)) */
+	acpigen_write_else();
+	acpigen_write_if_lequal_op_int(LOCAL0_OP,
+		ATIF_FUNCTION_QUERY_BRIGHTNESS_TRANSFER_CHARACTERISTICS);
+	/* CreateByteField (Arg1, 0x02, DISP) */
+	acpigen_write_create_byte_field(ARG1_OP,
+		offsetof(struct atif_brightness_input, requested_display), "DISP");
+	/* ToInteger (DISP, Local1) */
+	acpigen_write_to_integer_from_namestring("DISP", LOCAL1_OP);
+	/* If ((Local1 == Zero)) */
+	acpigen_write_if_lequal_op_int(LOCAL1_OP, ATIF_QBTC_REQUEST_LCD1);
+	/* Return (Buffer (0x0A) { ... } */
+	acpigen_write_return_byte_buffer((uint8_t *)(void *)&brightness_out,
+		sizeof(brightness_out));
+	acpigen_pop_len(); /* if (LEqual(Local2, ATIF_QBTC_REQUEST_LCD1) */
+	/* Else */
+	acpigen_write_else();
+	/* Return (Buffer (0x0A) */
+	acpigen_write_return_byte_buffer((uint8_t *)(void *)&brightness_error,
+		sizeof(brightness_error));
+	acpigen_pop_len(); /* else */
+
+	acpigen_pop_len(); /* if (LEqual(Local0, 0x10) */
+	acpigen_pop_len(); /* else */
+
+	acpigen_pop_len(); /* Method */
+	acpigen_pop_len(); /* Scope */
+}
+
 static void graphics_fill_ssdt(const struct device *dev)
 {
 	acpi_device_write_pci_dev(dev);
 	pci_rom_ssdt(dev);
+	if (CONFIG(SOC_AMD_COMMON_BLOCK_GRAPHICS_ATIF))
+		generate_atif(dev);
 }
 
 static const char *graphics_acpi_name(const struct device *dev)