iommu: introduce generic page table allocation framework

This patch introduces a generic framework for allocating page tables for
an IOMMU. There are a number of reasons we want to do this:

  - It avoids duplication of complex table management code in IOMMU
    drivers that use the same page table format

  - It removes any coupling with the CPU table format (and even the
    architecture!)

  - It defines an API for IOMMU TLB maintenance

Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 71 insertions, 0 deletions

diff --git a/drivers/iommu/io-pgtable.c b/drivers/iommu/io-pgtable.c
new file mode 100644
index 000000000000..f664a1ca49cf
--- /dev/null
+++ b/drivers/iommu/io-pgtable.c
@@ -0,0 +1,71 @@
+/*
+ * Generic page table allocator for IOMMUs.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright (C) 2014 ARM Limited
+ *
+ * Author: Will Deacon <will.deacon@arm.com>
+ */
+
+#include <linux/bug.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+
+#include "io-pgtable.h"
+
+static const struct io_pgtable_init_fns *
+io_pgtable_init_table[IO_PGTABLE_NUM_FMTS] =
+{
+};
+
+struct io_pgtable_ops *alloc_io_pgtable_ops(enum io_pgtable_fmt fmt,
+                                            struct io_pgtable_cfg *cfg,
+                                            void *cookie)
+{
+        struct io_pgtable *iop;
+        const struct io_pgtable_init_fns *fns;
+
+        if (fmt >= IO_PGTABLE_NUM_FMTS)
+                return NULL;
+
+        fns = io_pgtable_init_table[fmt];
+        if (!fns)
+                return NULL;
+
+        iop = fns->alloc(cfg, cookie);
+        if (!iop)
+                return NULL;
+
+        iop->fmt        = fmt;
+        iop->cookie     = cookie;
+        iop->cfg        = *cfg;
+
+        return &iop->ops;
+}
+
+/*
+ * It is the IOMMU driver's responsibility to ensure that the page table
+ * is no longer accessible to the walker by this point.
+ */
+void free_io_pgtable_ops(struct io_pgtable_ops *ops)
+{
+        struct io_pgtable *iop;
+
+        if (!ops)
+                return;
+
+        iop = container_of(ops, struct io_pgtable, ops);
+        iop->cfg.tlb->tlb_flush_all(iop->cookie);
+        io_pgtable_init_table[iop->fmt]->free(iop);
+}