[PATCH v4 2/6] misc: Generic on-chip SRAM allocation driver

[Philipp Zabel]

This driver requests and remaps a memory region as configured in the
device tree. It serves memory from this region via the genalloc API.

Other drivers can retrieve the genalloc pool from a phandle pointing
to this drivers' device node in the device tree.

Signed-off-by: Philipp Zabel <p.zabel at pengutronix.de>
Reviewed-by: Shawn Guo <shawn.guo at linaro.org>
---
Changes since v3:
 - Added devicetree binding documentation
 - Register platform driver with postcore_initcall
---
 Documentation/devicetree/bindings/misc/sram.txt |   17 ++++
 drivers/misc/Kconfig                            |    9 ++
 drivers/misc/Makefile                           |    1 +
 drivers/misc/sram.c                             |  111 +++++++++++++++++++++++
 4 files changed, 138 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/misc/sram.txt
 create mode 100644 drivers/misc/sram.c

diff --git a/Documentation/devicetree/bindings/misc/sram.txt b/Documentation/devicetree/bindings/misc/sram.txt
new file mode 100644
index 0000000..8bb26fc
--- /dev/null
+++ b/Documentation/devicetree/bindings/misc/sram.txt
@@ -0,0 +1,17 @@
+Generic on-chip SRAM
+
+Simple IO memory regions to be managed by the genalloc API.
+
+Required properties:
+
+- compatible : sram
+
+- reg : SRAM iomem address range
+
+Example:
+
+sram: sram at 5c000000 {
+	compatible = "sram";
+	reg = <0x5c000000 0x40000>; /* 256 KiB SRAM at address 0x5c000000 */
+};
+
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 98a442d..9a3395f 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -509,6 +509,15 @@ config USB_SWITCH_FSA9480
 	  stereo and mono audio, video, microphone and UART data to use
 	  a common connector port.
 
+config SRAM
+	bool "Generic on-chip SRAM driver"
+	depends on HAS_IOMEM
+	select GENERIC_ALLOCATOR
+	help
+	  This driver allows to declare a memory region to be managed
+	  by the genalloc API. It is supposed to be used for small
+	  on-chip SRAM areas found on many ARM SoCs.
+
 source "drivers/misc/c2port/Kconfig"
 source "drivers/misc/eeprom/Kconfig"
 source "drivers/misc/cb710/Kconfig"
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index b88df7a..ccc759a 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -50,3 +50,4 @@ obj-y				+= carma/
 obj-$(CONFIG_USB_SWITCH_FSA9480) += fsa9480.o
 obj-$(CONFIG_ALTERA_STAPL)	+=altera-stapl/
 obj-$(CONFIG_INTEL_MEI)		+= mei/
+obj-$(CONFIG_SRAM)		+= sram.o
diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
new file mode 100644
index 0000000..7a363f2
--- /dev/null
+++ b/drivers/misc/sram.c
@@ -0,0 +1,111 @@
+/*
+ * Generic on-chip SRAM allocation driver
+ *
+ * Copyright (C) 2012 Philipp Zabel, Pengutronix
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ * 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301, USA.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/spinlock.h>
+#include <linux/genalloc.h>
+
+struct sram_dev {
+	struct gen_pool *pool;
+};
+
+static int __devinit sram_probe(struct platform_device *pdev)
+{
+	void __iomem *virt_base;
+	struct sram_dev *sram;
+	struct resource *res;
+	unsigned long size;
+	int ret;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -EINVAL;
+
+	size = resource_size(res);
+
+	virt_base = devm_request_and_ioremap(&pdev->dev, res);
+	if (!virt_base)
+		return -EADDRNOTAVAIL;
+
+	sram = devm_kzalloc(&pdev->dev, sizeof(*sram), GFP_KERNEL);
+	if (!sram)
+		return -ENOMEM;
+
+	sram->pool = gen_pool_create(PAGE_SHIFT, -1);
+	if (!sram->pool)
+		return -ENOMEM;
+
+	ret = gen_pool_add_virt(sram->pool, (unsigned long)virt_base,
+				res->start, size, -1);
+	if (ret < 0) {
+		gen_pool_destroy(sram->pool);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, sram);
+
+	dev_dbg(&pdev->dev, "SRAM pool: %ld KiB @ 0x%p\n", size / 1024, virt_base);
+
+	return 0;
+}
+
+static int __devexit sram_remove(struct platform_device *pdev)
+{
+	struct sram_dev *sram = platform_get_drvdata(pdev);
+
+	if (gen_pool_avail(sram->pool) < gen_pool_size(sram->pool))
+		dev_dbg(&pdev->dev, "removed while SRAM allocated\n");
+
+	gen_pool_destroy(sram->pool);
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static struct of_device_id sram_dt_ids[] = {
+	{ .compatible = "sram" },
+	{ /* sentinel */ }
+};
+#endif
+
+static struct platform_driver sram_driver = {
+	.driver = {
+		.name = "sram",
+		.of_match_table = of_match_ptr(sram_dt_ids),
+	},
+	.probe = sram_probe,
+	.remove = __devexit_p(sram_remove),
+};
+
+int __init sram_init(void)
+{
+	return platform_driver_register(&sram_driver);
+}
+
+postcore_initcall(sram_init);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Philipp Zabel, Pengutronix");
+MODULE_DESCRIPTION("Generic SRAM allocator driver");
-- 
1.7.10.4