[PATCH V4 3/8] acpi: Adding DMA Attribute APIs for ACPI Device

[Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>]

Adding acpi_get_dma_attr() to query DMA attributes of ACPI devices.
It returns the enum dev_dma_attr, which communicates DMA information
more clearly. This API replaces the acpi_check_dma(), which will be
removed in subsequent patch.

This patch also provides a convenient function, acpi_dma_supported(),
to check DMA support of the specified ACPI device.

Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Rafael J. Wysocki <rjw@rjwysocki.net>
---
 drivers/acpi/scan.c     | 42 ++++++++++++++++++++++++++++++++++++++++++
 include/acpi/acpi_bus.h |  3 +++
 include/linux/acpi.h    | 10 ++++++++++
 3 files changed, 55 insertions(+)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 01136b8..3be213e 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1328,6 +1328,48 @@ void acpi_free_pnp_ids(struct acpi_device_pnp *pnp)
 	kfree(pnp->unique_id);
 }
 
+/**
+ * acpi_dma_supported - Check DMA support for the specified device.
+ * @adev: The pointer to acpi device
+ *
+ * Return false if DMA is not supported. Otherwise, return true
+ */
+bool acpi_dma_supported(struct acpi_device *adev)
+{
+	if (!adev)
+		return false;
+
+	if (adev->flags.cca_seen)
+		return true;
+
+	/*
+	* Per ACPI 6.0 sec 6.2.17, assume devices can do cache-coherent
+	* DMA on "Intel platforms".  Presumably that includes all x86 and
+	* ia64, and other arches will set CONFIG_ACPI_CCA_REQUIRED=y.
+	*/
+	if (!IS_ENABLED(CONFIG_ACPI_CCA_REQUIRED))
+		return true;
+
+	return false;
+}
+
+/**
+ * acpi_get_dma_attr - Check the supported DMA attr for the specified device.
+ * @adev: The pointer to acpi device
+ *
+ * Return enum dev_dma_attr.
+ */
+enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev)
+{
+	if (!acpi_dma_supported(adev))
+		return DEV_DMA_NOT_SUPPORTED;
+
+	if (adev->flags.coherent_dma)
+		return DEV_DMA_COHERENT;
+	else
+		return DEV_DMA_NON_COHERENT;
+}
+
 static void acpi_init_coherency(struct acpi_device *adev)
 {
 	unsigned long long cca = 0;
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 5a42204..13417d0 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -567,6 +567,9 @@ struct acpi_pci_root {
 
 /* helper */
 
+bool acpi_dma_supported(struct acpi_device *adev);
+enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev);
+
 struct acpi_device *acpi_find_child_device(struct acpi_device *parent,
 					   u64 address, bool check_children);
 int acpi_is_root_bridge(acpi_handle);
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index dd39202..c47892c 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -569,6 +569,16 @@ static inline bool acpi_check_dma(struct acpi_device *adev, bool *coherent)
 	return false;
 }
 
+static inline bool acpi_dma_supported(struct acpi_device *adev)
+{
+	return false;
+}
+
+static inline enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev)
+{
+	return DEV_DMA_NOT_SUPPORTED;
+}
+
 #define ACPI_PTR(_ptr)	(NULL)
 
 #endif	/* !CONFIG_ACPI */
-- 
2.1.0