Provide a helper to find the ACPI0017 device in order to issue the _DSM.
The helper will take the 'struct device' from a cxl_port and iterate until
the root device is reached. The ACPI handle will be returned from the root
device.
Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
---
drivers/cxl/core/acpi.c | 30 ++++++++++++++++++++++++++++++
drivers/cxl/cxl.h | 1 +
2 files changed, 31 insertions(+)
diff --git a/drivers/cxl/core/acpi.c b/drivers/cxl/core/acpi.c
index 86dc6c9c1f24..05fcd4751619 100644
--- a/drivers/cxl/core/acpi.c
+++ b/drivers/cxl/core/acpi.c
@@ -5,6 +5,7 @@
#include <linux/kernel.h>
#include <linux/acpi.h>
#include <linux/pci.h>
+#include <linux/platform_device.h>
#include <asm/div64.h>
#include "cxlpci.h"
#include "cxl.h"
@@ -13,6 +14,35 @@ const guid_t acpi_cxl_qtg_id_guid =
GUID_INIT(0xF365F9A6, 0xA7DE, 0x4071,
0xA6, 0x6A, 0xB4, 0x0C, 0x0B, 0x4F, 0x8E, 0x52);
+/**
+ * cxl_acpi_get_root_acpi_handle - get the ACPI handle of the CXL root device
+ * @dev: 'struct device' to start searching from. Should be from cxl_port->dev.
+ * Looks for the ACPI0017 device and return the ACPI handle
+ **/
+acpi_handle cxl_acpi_get_rootdev_handle(struct device *dev)
+{
+ struct device *itr = dev, *root_dev;
+ acpi_handle handle;
+
+ if (!dev)
+ return ERR_PTR(-EINVAL);
+
+ while (itr->parent) {
+ root_dev = itr;
+ itr = itr->parent;
+ }
+
+ if (!dev_is_platform(root_dev))
+ return ERR_PTR(-ENODEV);
+
+ handle = ACPI_HANDLE(root_dev);
+ if (!handle)
+ return ERR_PTR(-ENODEV);
+
+ return handle;
+}
+EXPORT_SYMBOL_NS_GPL(cxl_acpi_get_rootdev_handle, CXL);
+
/**
* cxl_acpi_evaluate_qtg_dsm - Retrieve QTG ids via ACPI _DSM
* @handle: ACPI handle
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index e70df07f9b4b..ac6ea550ab0a 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -733,6 +733,7 @@ struct qtg_dsm_output {
struct qtg_dsm_output *cxl_acpi_evaluate_qtg_dsm(acpi_handle handle,
struct qtg_dsm_input *input);
+acpi_handle cxl_acpi_get_rootdev_handle(struct device *dev);
/*
* Unit test builds overrides this to __weak, find the 'strong' version
