Changeset 3e6ff9a in mainline

Timestamp:

2018-02-01T14:28:41Z (7 years ago)

Author:

Ondřej Hlavatý <aearsis@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

e67c50a

Parents:

77ded647

Message:

usb: dma_buffer check policy function

Location:

uspace/lib/usb

Files:

• include/usb/dma_buffer.h (modified) (3 diffs)
• src/dma_buffer.c (modified) (4 diffs)

uspace/lib/usb/include/usb/dma_buffer.h

@@ -32 +32 @@
  * @brief USB host controller library: DMA buffer helpers
  *
- * Simplifies usage of bounce buffers.
+ * Simplifies usage of bounce buffers
  *
  * Currently the minimum size allocated is a page, which is wasteful. Could be
@@ -46 +46 @@
 
 typedef const struct dma_policy {
-        bool use64;             /**< Whether to use more than initial 4GiB of memory */
-        size_t alignment;       /**< What alignment is needed. At most PAGE_SIZE. */
+        unsigned flags;
+
+#define DMA_POLICY_F_4GiB       (1<<0)  /**< Must use only 32-bit addresses */
+#define DMA_POLICY_F_CONTIGUOUS (1<<1)  /**< Pages must follow each other physically */
 } dma_policy_t;
 
@@ -56 +58 @@
 
 extern int dma_buffer_alloc(dma_buffer_t *db, size_t size);
-extern int dma_buffer_alloc_policy(dma_buffer_t *, size_t, const dma_policy_t *);
+extern int dma_buffer_alloc_policy(dma_buffer_t *, size_t, dma_policy_t *);
 extern void dma_buffer_free(dma_buffer_t *);
 extern uintptr_t dma_buffer_phys(const dma_buffer_t *, void *);
+
+extern bool dma_buffer_check_policy(const void *, size_t, dma_policy_t *);
 
 static inline int dma_buffer_is_set(dma_buffer_t *db)

uspace/lib/usb/src/dma_buffer.c

@@ -40 +40 @@
 
 const dma_policy_t dma_policy_default = {
-        .use64 = false,
-        .alignment = PAGE_SIZE,
+        .flags = DMA_POLICY_F_4GiB | DMA_POLICY_F_CONTIGUOUS,
 };
 
@@ -47 +46 @@
  * The routine of allocating a DMA buffer. Inlined to force optimization for the
  * default policy.
+ *
+ * FIXME: We ignore the non-presence of contiguous flag, for now.
  */
 static inline int dma_buffer_alloc_internal(dma_buffer_t *db,
@@ -53 +54 @@
         assert(db);
 
-        if (policy->alignment > PAGE_SIZE)
-                return EINVAL;
+        const size_t real_size = ALIGN_UP(size, PAGE_SIZE);
+        const bool need_4gib = !!(policy->flags & DMA_POLICY_F_4GiB);
 
-        const size_t aligned_size = ALIGN_UP(size, policy->alignment);
-        const size_t real_size = ALIGN_UP(aligned_size, PAGE_SIZE);
-        const uintptr_t flags = policy->use64 ? 0 : DMAMEM_4GiB;
+        const uintptr_t flags = need_4gib ? DMAMEM_4GiB : 0;
 
         uintptr_t phys;
@@ -127 +126 @@
 
 /**
+ * Check whether a memory area is compatible with a policy.
+ *
+ * Useful to skip copying, if the buffer is already ready to be given to
+ * hardware.
+ */
+bool dma_buffer_check_policy(const void *buffer, size_t size, dma_policy_t *policy)
+{
+        /* Buffer must be always page aligned */
+        if (((uintptr_t) buffer) % PAGE_SIZE)
+                goto violated;
+
+        const bool check_4gib = !!(policy->flags & DMA_POLICY_F_4GiB);
+        const bool check_contiguous = !!(policy->flags & DMA_POLICY_F_CONTIGUOUS);
+
+        /*
+         * For these conditions, we need to walk through pages and check
+         * physical address of each one
+         */
+        if (check_contiguous || check_4gib) {
+                const void * virt = buffer;
+                uintptr_t phys;
+
+                /* Get the mapping of the first page */
+                if (as_get_physical_mapping(virt, &phys))
+                        goto error;
+
+                /* First page can already break 4GiB condition */
+                if (check_4gib && (phys & DMAMEM_4GiB) != 0)
+                        goto violated;
+
+                while (size <= PAGE_SIZE) {
+                        /* Move to the next page */
+                        virt += PAGE_SIZE;
+                        size -= PAGE_SIZE;
+
+                        uintptr_t last_phys = phys;
+                        if (as_get_physical_mapping(virt, &phys))
+                                goto error;
+
+                        if (check_contiguous && (phys - last_phys) != PAGE_SIZE)
+                                goto violated;
+
+                        if (check_4gib && (phys & DMAMEM_4GiB) != 0)
+                                goto violated;
+                }
+        }
+
+        /* All checks passed */
+        return true;
+
+violated:
+error:
+        return false;
+}
+
+/**
  * @}
  */