ACPI / scan: Parse _CCA and setup device coherency

This patch implements support for ACPI _CCA object, which is introduced in
ACPIv5.1, can be used for specifying device DMA coherency attribute.

The parsing logic traverses device namespace to parse coherency
information, and stores it in acpi_device_flags. Then uses it to call
arch_setup_dma_ops() when creating each device enumerated in DSDT
during ACPI scan.

This patch also introduces acpi_dma_is_coherent(), which provides
an interface for device drivers to check the coherency information
similarly to the of_dma_is_coherent().

Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 41 insertions, 1 deletions

diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index da079976971f..54df54d00cd2 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -209,7 +209,9 @@ struct acpi_device_flags {
 	u32 hotplug_notify:1;
 	u32 is_dock_station:1;
 	u32 of_compatible_ok:1;
-	u32 reserved:22;
+	u32 coherent_dma:1;
+	u32 cca_seen:1;
+	u32 reserved:20;
 };
 
 /* File System */
@@ -381,6 +383,39 @@ struct acpi_device {
 	void (*remove)(struct acpi_device *);
 };
 
+static inline bool acpi_check_dma(struct acpi_device *adev, bool *coherent)
+{
+	bool ret = false;
+
+	if (!adev)
+		return ret;
+
+	/**
+	 * Currently, we only support _CCA=1 (i.e. coherent_dma=1)
+	 * This should be equivalent to specifyig dma-coherent for
+	 * a device in OF.
+	 *
+	 * For the case when _CCA=0 (i.e. coherent_dma=0 && cca_seen=1),
+	 * There are two cases:
+	 * case 1. Do not support and disable DMA.
+	 * case 2. Support but rely on arch-specific cache maintenance for
+	 *         non-coherence DMA operations.
+	 * Currently, we implement case 1 above.
+	 *
+	 * For the case when _CCA is missing (i.e. cca_seen=0) and
+	 * platform specifies ACPI_CCA_REQUIRED, we do not support DMA,
+	 * and fallback to arch-specific default handling.
+	 *
+	 * See acpi_init_coherency() for more info.
+	 */
+	if (adev->flags.coherent_dma) {
+		ret = true;
+		if (coherent)
+			*coherent = adev->flags.coherent_dma;
+	}
+	return ret;
+}
+
 static inline bool is_acpi_node(struct fwnode_handle *fwnode)
 {
 	return fwnode && fwnode->type == FWNODE_ACPI;
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index e4da5e35e29c..d46a48c21c67 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -569,6 +569,11 @@ static inline int acpi_device_modalias(struct device *dev,
 	return -ENODEV;
 }
 
+static inline bool acpi_check_dma(struct acpi_device *adev, bool *coherent)
+{
+	return false;
+}
+
 #define ACPI_PTR(_ptr)	(NULL)
 
 #endif	/* !CONFIG_ACPI */