[PATCH v5 1/5] misc: sram: add ability to limit used sram areas

[heiko@sntech.de (Heiko Stübner)]

Some SoCs need parts of their sram for special purposes. So while being part
of the peripheral, it should not be part of the genpool controlling the sram.

Therefore add an option available to keep arbitrary portions of the
sram from being part of the pool. If available is not present, all
sram is used.

Suggested-by: Rob Herring <robherring2@gmail.com>
move from marking reserved space to available space
Suggested-by: Matt Sealey <neko@bakuhatsu.net>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Ulrich Prinz <ulrich.prinz@googlemail.com>
---
 Documentation/devicetree/bindings/misc/sram.txt |    8 ++++
 drivers/misc/sram.c                             |   51 ++++++++++++++++++++---
 2 files changed, 53 insertions(+), 6 deletions(-)

diff --git a/Documentation/devicetree/bindings/misc/sram.txt b/Documentation/devicetree/bindings/misc/sram.txt
index 4d0a00e..8be552f 100644
--- a/Documentation/devicetree/bindings/misc/sram.txt
+++ b/Documentation/devicetree/bindings/misc/sram.txt
@@ -8,9 +8,17 @@ Required properties:
 
 - reg : SRAM iomem address range
 
+Optional properties:
+
+- available: optional list of available chunks inside the sram that the
+  OS can use. Without available, the whole range is usable for the OS.
+  Format is <base size>, <base size>, ...; with base being relative to the
+  reg property base.
+
 Example:
 
 sram: sram at 5c000000 {
 	compatible = "mmio-sram";
 	reg = <0x5c000000 0x40000>; /* 256 KiB SRAM at address 0x5c000000 */
+	available = <0x100 0x3ff00>;
 };
diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
index afe66571..755e640 100644
--- a/drivers/misc/sram.c
+++ b/drivers/misc/sram.c
@@ -42,6 +42,8 @@ static int sram_probe(struct platform_device *pdev)
 	struct sram_dev *sram;
 	struct resource *res;
 	unsigned long size;
+	const __be32 *avail_list = NULL;
+	int avail_size = 0;
 	int ret;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
@@ -65,12 +67,49 @@ static int sram_probe(struct platform_device *pdev)
 	if (!sram->pool)
 		return -ENOMEM;
 
-	ret = gen_pool_add_virt(sram->pool, (unsigned long)virt_base,
-				res->start, size, -1);
-	if (ret < 0) {
-		if (sram->clk)
-			clk_disable_unprepare(sram->clk);
-		return ret;
+	if (pdev->dev.of_node) {
+		avail_list = of_get_property(pdev->dev.of_node,
+						"available",
+						&avail_size);
+		if (avail_list) {
+			avail_size /= sizeof(*avail_list);
+			if (!avail_size || avail_size % 2) {
+				dev_warn(&pdev->dev, "wrong number of arguments in available property\n");
+				avail_list = NULL;
+			}
+		}
+	}
+
+	if (!avail_list) {
+		ret = gen_pool_add_virt(sram->pool, (unsigned long)virt_base,
+					res->start, size, -1);
+		if (ret < 0) {
+			if (sram->clk)
+				clk_disable_unprepare(sram->clk);
+			return ret;
+		}
+	} else {
+		unsigned int astart;
+		unsigned int asize;
+		int i;
+
+		for (i = 0; i < avail_size; i += 2) {
+			/* get the next available block */
+			astart = be32_to_cpu(*avail_list++);
+			asize = be32_to_cpu(*avail_list++);
+
+			dev_dbg(&pdev->dev, "found available block 0x%x-0x%x\n",
+				 astart, astart + asize);
+
+			ret = gen_pool_add_virt(sram->pool,
+					(unsigned long)virt_base + astart,
+					res->start + astart, asize, -1);
+			if (ret < 0) {
+				if (sram->clk)
+					clk_disable_unprepare(sram->clk);
+				return ret;
+			}
+		}
 	}
 
 	platform_set_drvdata(pdev, sram);
-- 
1.7.10.4