Introduce the new compatible string, bounced-dma-pool, for bounced DMA.
One can specify the address and length of the bounced memory region by
bounced-dma-pool in the device tree.
Signed-off-by: Claire Chang <tien...@chromium.org>
---
.../reserved-memory/reserved-memory.txt | 36 +++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git
a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
index 4dd20de6977f..45b3134193ea 100644
--- a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
+++ b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
@@ -51,6 +51,24 @@ compatible (optional) - standard definition
used as a shared pool of DMA buffers for a set of devices. It can
be used by an operating system to instantiate the necessary pool
management subsystem if necessary.
+ - bounced-dma-pool: This indicates a region of memory meant to be used
+ as a pool of DMA bounce buffers for a given device. When using this,
+ the no-map and reusable properties must not be set, so the operating
+ system can create a virtual mapping that will be used for
+ synchronization. Also, there must be a bounced-dma property in the
+ device node to specify the indexes of reserved-memory nodes. One can
+ specify two reserved-memory nodes in the device tree. One with
+ shared-dma-pool to handle the coherent DMA buffer allocation, and
+ another one with bounced-dma-pool for regular DMA to/from system
+ memory, which would be subject to bouncing. The main purpose for
+ bounced DMA is to mitigate the lack of DMA access control on systems
+ without an IOMMU, which could result in the DMA accessing the system
+ memory at unexpected times and/or unexpected addresses, possibly
+ leading to data leakage or corruption. The feature on its own
provides
+ a basic level of protection against the DMA overwriting buffer
+ contents at unexpected times. However, to protect against general
data
+ leakage and system memory corruption, the system needs to provide a
+ way to restrict the DMA to a predefined memory region.
- vendor specific string in the form <vendor>,[<device>-]<usage>
no-map (optional) - empty property
- Indicates the operating system must not create a virtual mapping
@@ -117,6 +135,17 @@ one for multimedia processing (named
multimedia-memory@77000000, 64MiB).
compatible = "acme,multimedia-memory";
reg = <0x77000000 0x4000000>;
};
+
+ wifi_bounced_dma_mem_region: wifi_bounced_dma_mem_region {
+ compatible = "bounced-dma-pool";
+ reg = <0x50000000 0x4000000>;
+ };
+
+ wifi_coherent_mem_region: wifi_coherent_mem_region {
+ compatible = "shared-dma-pool";
+ reg = <0x54000000 0x400000>;
+ };
+
};
/* ... */
@@ -135,4 +164,11 @@ one for multimedia processing (named
multimedia-memory@77000000, 64MiB).
memory-region = <&multimedia_reserved>;
/* ... */
};
+
+ pcie_wifi: pcie_wifi@0,0 {
+ memory-region = <&wifi_bounced_dma_mem_region>,
+ <&wifi_coherent_mem_region>;
+ bounced-dma = <0>, <1>;
+ /* ... */
+ };
};
--
2.27.0.383.g050319c2ae-goog
