habanalabs: add command buffer module

This patch adds the command buffer (CB) module, which allows the user to
create and destroy CBs and to map them to the user's process
address-space.

A command buffer is a memory blocks that reside in DMA-able address-space
and is physically contiguous so it can be accessed by the device without
MMU translation. The command buffer memory is allocated using the
coherent DMA API.

When creating a new CB, the IOCTL returns a handle of it, and the
user-space process needs to use that handle to mmap the buffer to get a VA
in the user's address-space.

Before destroying (freeing) a CB, the user must unmap the CB's VA using the
CB handle.

Each CB has a reference counter, which tracks its usage in command
submissions and also its mmaps (only a single mmap is allowed).

The driver maintains a pool of pre-allocated CBs in order to reduce
latency during command submissions. In case the pool is empty, the driver
will go to the slow-path of allocating a new CB, i.e. calling
dma_alloc_coherent.

Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 46 insertions, 0 deletions

diff --git a/include/uapi/misc/habanalabs.h b/include/uapi/misc/habanalabs.h
index a0ec23adf8f5..a8edfd3e9c95 100644
--- a/include/uapi/misc/habanalabs.h
+++ b/include/uapi/misc/habanalabs.h
@@ -17,4 +17,50 @@
  */
 #define GOYA_KMD_SRAM_RESERVED_SIZE_FROM_START	0x8000	/* 32KB */
 
+/* Opcode to create a new command buffer */
+#define HL_CB_OP_CREATE		0
+/* Opcode to destroy previously created command buffer */
+#define HL_CB_OP_DESTROY	1
+
+struct hl_cb_in {
+	/* Handle of CB or 0 if we want to create one */
+	__u64 cb_handle;
+	/* HL_CB_OP_* */
+	__u32 op;
+	/* Size of CB. Minimum requested size must be PAGE_SIZE */
+	__u32 cb_size;
+	/* Context ID - Currently not in use */
+	__u32 ctx_id;
+	__u32 pad;
+};
+
+struct hl_cb_out {
+	/* Handle of CB */
+	__u64 cb_handle;
+};
+
+union hl_cb_args {
+	struct hl_cb_in in;
+	struct hl_cb_out out;
+};
+
+/*
+ * Command Buffer
+ * - Request a Command Buffer
+ * - Destroy a Command Buffer
+ *
+ * The command buffers are memory blocks that reside in DMA-able address
+ * space and are physically contiguous so they can be accessed by the device
+ * directly. They are allocated using the coherent DMA API.
+ *
+ * When creating a new CB, the IOCTL returns a handle of it, and the user-space
+ * process needs to use that handle to mmap the buffer so it can access them.
+ *
+ */
+#define HL_IOCTL_CB		\
+		_IOWR('H', 0x02, union hl_cb_args)
+
+#define HL_COMMAND_START	0x02
+#define HL_COMMAND_END		0x03
+
 #endif /* HABANALABS_H_ */