linux-kernel - [PATCH 5/5] misc: sram: add Atmel securam support

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Date:   Wed, 31 Aug 2016 18:11:08 +0200
From:   Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:     Nicolas Ferre <nicolas.ferre@...el.com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
Subject: [PATCH 5/5] misc: sram: add Atmel securam support

The Atmel secure SRAM is connected to a security module and may be erased
automatically under certain conditions. For that reason, it is necessary to
wait for the security module to flag that SRAM accesses are allowed before
accessing it.

Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
---
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Philipp Zabel <p.zabel@...gutronix.de>
Cc: Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
 drivers/misc/sram.c | 52 +++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 45 insertions(+), 7 deletions(-)

diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
index f84b53d6ce50..8d411c64d07f 100644
--- a/drivers/misc/sram.c
+++ b/drivers/misc/sram.c
@@ -19,12 +19,16 @@
  */
 
 #include <linux/clk.h>
+#include <linux/delay.h>
 #include <linux/genalloc.h>
 #include <linux/io.h>
 #include <linux/list_sort.h>
 #include <linux/of_address.h>
 #include <linux/platform_device.h>
+#include <linux/regmap.h>
 #include <linux/slab.h>
+#include <linux/mfd/syscon.h>
+#include <soc/at91/atmel-secumod.h>
 
 #define SRAM_GRANULARITY	32
 
@@ -334,12 +338,43 @@ static int sram_reserve_regions(struct sram_dev *sram, struct resource *res)
 	return ret;
 }
 
+static int atmel_securam_wait(void)
+{
+	struct regmap *regmap;
+	unsigned long timeout = jiffies + HZ;
+	u32 val;
+
+	regmap = syscon_regmap_lookup_by_compatible("atmel,sama5d2-secumod");
+	if (IS_ERR(regmap))
+		return -ENODEV;
+
+	regmap_read(regmap, AT91_SECUMOD_RAMRDY, &val);
+	while (!(val & AT91_SECUMOD_RAMRDY_READY) &&
+	       time_before(jiffies, timeout)) {
+		mdelay(10);
+		regmap_read(regmap, AT91_SECUMOD_RAMRDY, &val);
+	}
+	if (!time_before(jiffies, timeout))
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id sram_dt_ids[] = {
+	{ .compatible = "mmio-sram" },
+	{ .compatible = "atmel,sama5d2-securam", .data = atmel_securam_wait },
+	{}
+};
+#endif
+
 static int sram_probe(struct platform_device *pdev)
 {
 	struct sram_dev *sram;
 	struct resource *res;
 	size_t size;
 	int ret;
+	const struct of_device_id *match;
 
 	sram = devm_kzalloc(&pdev->dev, sizeof(*sram), GFP_KERNEL);
 	if (!sram)
@@ -384,6 +419,16 @@ static int sram_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, sram);
 
+	match = of_match_node(sram_dt_ids, pdev->dev.of_node);
+	if (match->data) {
+		int (*init_func)(void);
+
+		init_func = match->data;
+		ret = init_func();
+		if (ret)
+			return ret;
+	}
+
 	dev_dbg(sram->dev, "SRAM pool: %zu KiB @ 0x%p\n",
 		gen_pool_size(sram->pool) / 1024, sram->virt_base);
 
@@ -405,13 +450,6 @@ static int sram_remove(struct platform_device *pdev)
 	return 0;
 }
 
-#ifdef CONFIG_OF
-static const struct of_device_id sram_dt_ids[] = {
-	{ .compatible = "mmio-sram" },
-	{}
-};
-#endif
-
 static struct platform_driver sram_driver = {
 	.driver = {
 		.name = "sram",
-- 
2.9.3