[PATCH v3 4/7] DSPBRIDGE: do not use low level cache manipulation API

[Ohad Ben-Cohen <ohad@wizery.com>]

Instead of using low level cache manipulation API,
use the standard DMA API. This is achieved by adding
a proc_begin_dma function that takes a generic
dma_data_direction, and then implementing proc_flush_memory
and proc_invalidate_memory by means of proc_begin_dma
in the following manner:

* flush calls proc_begin_dma with DMA_BIDIRECTIONAL
* Invalidate calls proc_begin_dma with DMA_FROM_DEVICE

proc_begin_dma builds a scatter gatter list using the
page information that was kept during proc_map,
and feed it to the standard dma_map_sg API.

Note that now users cannot manipulate the cache state of any random
address; if the buffer is not part of a previous memory mapping of that
application, the request is denied.

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
---
If you want, you can also reach me at <  ohadb at ti dot com  >.

 arch/arm/plat-omap/include/dspbridge/drv.h |   13 +++
 drivers/dsp/bridge/rmgr/proc.c             |  119 +++++++++++++++++++++-------
 2 files changed, 104 insertions(+), 28 deletions(-)

diff --git a/arch/arm/plat-omap/include/dspbridge/drv.h b/arch/arm/plat-omap/include/dspbridge/drv.h
index b1312aa..3186935 100644
--- a/arch/arm/plat-omap/include/dspbridge/drv.h
+++ b/arch/arm/plat-omap/include/dspbridge/drv.h
@@ -84,6 +84,18 @@ struct node_res_object {
 	struct node_res_object *next;
 };
 
+/* used to cache dma mapping information */
+struct bridge_dma_map_info {
+	/* direction of DMA in action, or DMA_NONE */
+	enum dma_data_direction dir;
+	/* number of elements requested by us */
+	int num_pages;
+	/* number of elements returned from dma_map_sg */
+	int sg_num;
+	/* list of buffers used in this DMA action */
+	struct scatterlist *sg;
+};
+
 /* Used for DMM mapped memory accounting */
 struct dmm_map_object {
 	struct list_head link;
@@ -92,6 +104,7 @@ struct dmm_map_object {
 	u32 size;
 	u32 num_usr_pgs;
 	struct page **pages;
+	struct bridge_dma_map_info dma_info;
 };
 
 /* Used for DMM reserved memory accounting */
diff --git a/drivers/dsp/bridge/rmgr/proc.c b/drivers/dsp/bridge/rmgr/proc.c
index 6628483..2710a11 100644
--- a/drivers/dsp/bridge/rmgr/proc.c
+++ b/drivers/dsp/bridge/rmgr/proc.c
@@ -17,6 +17,8 @@
  */
 
 /* ------------------------------------ Host OS */
+#include <linux/dma-mapping.h>
+#include <linux/scatterlist.h>
 #include <dspbridge/host_os.h>
 
 /*  ----------------------------------- DSP/BIOS Bridge */
@@ -74,6 +76,8 @@
 #define RBUF		0x4000		/* Input buffer */
 #define WBUF		0x8000		/* Output Buffer */
 
+extern struct device *bridge;
+
 /*  ----------------------------------- Globals */
 
 /* The proc_object structure. */
@@ -177,6 +181,7 @@ static void remove_mapping_information(struct process_context *pr_ctxt,
 		if (match_exact_map_obj(map_obj, dsp_addr, size)) {
 			pr_debug("%s: match, deleting map info\n", __func__);
 			list_del(&map_obj->link);
+			kfree(map_obj->dma_info.sg);
 			kfree(map_obj->pages);
 			kfree(map_obj);
 			goto out;
@@ -606,49 +611,108 @@ dsp_status proc_enum_nodes(void *hprocessor, void **node_tab,
 }
 
 /* Cache operation against kernel address instead of users */
-static int memory_sync_page(struct dmm_map_object *map_obj,
-		unsigned long start, ssize_t len, enum dsp_flushtype ftype)
+static int build_dma_sg(struct dmm_map_object *map_obj, unsigned long start,
+						ssize_t len, int pg_i)
 {
 	struct page *page;
-	void *kaddr;
 	unsigned long offset;
 	ssize_t rest;
-	int pg_i;
-
-	pg_i = find_first_page_in_cache(map_obj, start);
-	if (pg_i < 0) {
-		pr_err("%s: failed to find first page in cache\n", __func__);
-		return -EINVAL;
-	}
+	int ret = 0, i = 0;
+	struct scatterlist *sg = map_obj->dma_info.sg;
 
 	while (len) {
 		page = get_mapping_page(map_obj, pg_i);
 		if (!page) {
 			pr_err("%s: no page for %08lx\n", __func__, start);
-			return -EINVAL;
+			ret = -EINVAL;
+			goto out;
 		} else if (IS_ERR(page)) {
 			pr_err("%s: err page for %08lx(%lu)\n", __func__, start,
 			       PTR_ERR(page));
-			return PTR_ERR(page);
+			ret = PTR_ERR(page);
+			goto out;
 		}
 
 		offset = start & ~PAGE_MASK;
-		kaddr = kmap(page) + offset;
 		rest = min_t(ssize_t, PAGE_SIZE - offset, len);
-		mem_flush_cache(kaddr, rest, ftype);
 
-		kunmap(page);
+		sg_set_page(&sg[i], page, rest, offset);
+
 		len -= rest;
 		start += rest;
-		pg_i++;
+		pg_i++, i++;
 	}
 
+	if (i != map_obj->dma_info.num_pages) {
+		pr_err("%s: bad number of sg iterations\n", __func__);
+		ret = -EFAULT;
+		goto out;
+	}
+
+out:
+	return ret;
+}
+
+/* Cache operation against kernel address instead of users */
+static int memory_give_ownership(struct dmm_map_object *map_obj,
+		unsigned long start, ssize_t len, enum dma_data_direction dir)
+{
+	int pg_i, ret, sg_num;
+	struct scatterlist *sg;
+	unsigned long first_data_page = start >> PAGE_SHIFT;
+	unsigned long last_data_page = ((u32)(start + len - 1) >> PAGE_SHIFT);
+	/* calculating the number of pages this area spans */
+	unsigned long num_pages = last_data_page - first_data_page + 1;
+
+	pg_i = find_first_page_in_cache(map_obj, start);
+	if (pg_i < 0) {
+		pr_err("%s: failed to find first page in cache\n", __func__);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	sg = kcalloc(num_pages, sizeof(*sg), GFP_KERNEL);
+	if (!sg) {
+		pr_err("%s: kcalloc failed\n", __func__);
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	sg_init_table(sg, num_pages);
+
+	/* cleanup a previous sg allocation */
+	/* this may happen if application doesn't signal for e/o DMA */
+	kfree(map_obj->dma_info.sg);
+
+	map_obj->dma_info.sg = sg;
+	map_obj->dma_info.dir = dir;
+	map_obj->dma_info.num_pages = num_pages;
+
+	ret = build_dma_sg(map_obj, start, len, pg_i);
+	if (ret)
+		goto kfree_sg;
+
+	sg_num = dma_map_sg(bridge, sg, num_pages, dir);
+	if (sg_num < 1) {
+		pr_err("%s: dma_map_sg failed: %d\n", __func__, sg_num);
+		ret = -EFAULT;
+		goto kfree_sg;
+	}
+
+	pr_debug("%s: dma_map_sg mapped %d elements\n", __func__, sg_num);
+	map_obj->dma_info.sg_num = sg_num;
+
 	return 0;
+
+kfree_sg:
+	kfree(sg);
+	map_obj->dma_info.sg = NULL;
+out:
+	return ret;
 }
 
-static dsp_status proc_memory_sync(void *hprocessor, void *pmpu_addr,
-				   u32 ul_size, u32 ul_flags,
-				   enum dsp_flushtype FlushMemType)
+static int proc_begin_dma(void *hprocessor, void *pmpu_addr, u32 ul_size,
+				enum dma_data_direction dir)
 {
 	/* Keep STATUS here for future additions to this function */
 	dsp_status status = DSP_SOK;
@@ -664,7 +728,7 @@ static dsp_status proc_memory_sync(void *hprocessor, void *pmpu_addr,
 
 	pr_debug("%s: addr 0x%x, size 0x%x, type %d\n", __func__,
 							(u32)pmpu_addr,
-							ul_size, ul_flags);
+							ul_size, dir);
 
 	/* find requested memory are in cached mapping information */
 	map_obj = find_containing_mapping(pr_ctxt, (u32) pmpu_addr, ul_size);
@@ -673,7 +737,8 @@ static dsp_status proc_memory_sync(void *hprocessor, void *pmpu_addr,
 		status = -EFAULT;
 		goto err_out;
 	}
-	if (memory_sync_page(map_obj, (u32) pmpu_addr, ul_size, ul_flags)) {
+
+	if (memory_give_ownership(map_obj, (u32) pmpu_addr, ul_size, dir)) {
 		pr_err("%s: InValid address parameters %p %x\n",
 			       __func__, pmpu_addr, ul_size);
 		status = -EFAULT;
@@ -692,10 +757,9 @@ err_out:
 dsp_status proc_flush_memory(void *hprocessor, void *pmpu_addr,
 			     u32 ul_size, u32 ul_flags)
 {
-	enum dsp_flushtype mtype = PROC_WRITEBACK_INVALIDATE_MEM;
+	enum dma_data_direction dir = DMA_BIDIRECTIONAL;
 
-	return proc_memory_sync(hprocessor, pmpu_addr, ul_size, ul_flags,
-				mtype);
+	return proc_begin_dma(hprocessor, pmpu_addr, ul_size, dir);
 }
 
 /*
@@ -703,12 +767,11 @@ dsp_status proc_flush_memory(void *hprocessor, void *pmpu_addr,
  *  Purpose:
  *     Invalidates the memory specified
  */
-dsp_status proc_invalidate_memory(void *hprocessor, void *pmpu_addr,
-				  u32 ul_size)
+dsp_status proc_invalidate_memory(void *hprocessor, void *pmpu_addr, u32 size)
 {
-	enum dsp_flushtype mtype = PROC_INVALIDATE_MEM;
+	enum dma_data_direction dir = DMA_FROM_DEVICE;
 
-	return proc_memory_sync(hprocessor, pmpu_addr, ul_size, 0, mtype);
+	return proc_begin_dma(hprocessor, pmpu_addr, size, dir);
 }
 
 /*
-- 
1.7.0.4