kern: dma: Add DMA frame allocator

Introduce a special frame allocation utility to reserve memory for
DMA done between devices and the host.

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 76 insertions, 0 deletions

diff --git a/src/sys/io/dma/alloc.c b/src/sys/io/dma/alloc.c
new file mode 100644
index 0000000..3322879
--- /dev/null
+++ b/src/sys/io/dma/alloc.c
@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the project nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/syslog.h>
+#include <io/dma/alloc.h>
+#include <vm/physseg.h>
+#include <vm/mmu.h>
+#include <vm/map.h>
+#include <vm/vm.h>
+
+/*
+ * Allocate DMA pages
+ */
+void *
+dma_alloc_pg(size_t npages)
+{
+    struct vm_vas vas;
+    struct mmu_map spec;
+    size_t length;
+    int error, prot;
+    void *buf = NULL;
+    paddr_t pa;
+
+    if ((pa = vm_alloc_frame(npages)) == 0) {
+        return NULL;
+    }
+
+    spec.pa = pa;
+    spec.va = pa;
+    length = DEFAULT_PAGESIZE * npages;
+
+    /* Try to get the current VAS */
+    error = mmu_this_vas(&vas);
+    if (error < 0) {
+        goto done;
+    }
+
+    /* Map the region */
+    prot = PROT_READ | PROT_WRITE;
+    error = vm_map(&vas, &spec, length, prot);
+    if (error < 0) {
+        goto done;
+    }
+
+    buf = (void *)spec.va;
+done:
+    return buf;
+}