hwrng: msm - Add PRNG support for MSM SoC's

This adds a driver for hardware random number generator present
on Qualcomm MSM SoC's.
Signed-off-by: Stanimir Varbanov <svarbanov@mm-sol.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/Kconfig

@@ -327,3 +327,15 @@ config HW_RANDOM_TPM
 	  module will be called tpm-rng.
 
 	  If unsure, say Y.
+
+config HW_RANDOM_MSM
+	tristate "Qualcomm MSM Random Number Generator support"
+	depends on HW_RANDOM && ARCH_MSM
+	---help---
+	  This driver provides kernel-side support for the Random Number
+	  Generator hardware found on Qualcomm MSM SoCs.
+
+	  To compile this driver as a module, choose M here. the
+	  module will be called msm-rng.
+
+	  If unsure, say Y.

drivers/char/hw_random/Makefile

@@ -28,3 +28,4 @@ obj-$(CONFIG_HW_RANDOM_PSERIES) += pseries-rng.o
 obj-$(CONFIG_HW_RANDOM_EXYNOS)	+= exynos-rng.o
 obj-$(CONFIG_HW_RANDOM_TPM) += tpm-rng.o
 obj-$(CONFIG_HW_RANDOM_BCM2835) += bcm2835-rng.o
+obj-$(CONFIG_HW_RANDOM_MSM) += msm-rng.o

drivers/char/hw_random/msm-rng.c

+/*
+ * Copyright (c) 2011-2013, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only 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.
+ *
+ */
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+/* Device specific register offsets */
+#define PRNG_DATA_OUT		0x0000
+#define PRNG_STATUS		0x0004
+#define PRNG_LFSR_CFG		0x0100
+#define PRNG_CONFIG		0x0104
+
+/* Device specific register masks and config values */
+#define PRNG_LFSR_CFG_MASK	0x0000ffff
+#define PRNG_LFSR_CFG_CLOCKS	0x0000dddd
+#define PRNG_CONFIG_HW_ENABLE	BIT(1)
+#define PRNG_STATUS_DATA_AVAIL	BIT(0)
+
+#define MAX_HW_FIFO_DEPTH	16
+#define MAX_HW_FIFO_SIZE	(MAX_HW_FIFO_DEPTH * 4)
+#define WORD_SZ			4
+
+struct msm_rng {
+	void __iomem *base;
+	struct clk *clk;
+	struct hwrng hwrng;
+};
+
+#define to_msm_rng(p)	container_of(p, struct msm_rng, hwrng)
+
+static int msm_rng_enable(struct hwrng *hwrng, int enable)
+{
+	struct msm_rng *rng = to_msm_rng(hwrng);
+	u32 val;
+	int ret;
+
+	ret = clk_prepare_enable(rng->clk);
+	if (ret)
+		return ret;
+
+	if (enable) {
+		/* Enable PRNG only if it is not already enabled */
+		val = readl_relaxed(rng->base + PRNG_CONFIG);
+		if (val & PRNG_CONFIG_HW_ENABLE)
+			goto already_enabled;
+
+		val = readl_relaxed(rng->base + PRNG_LFSR_CFG);
+		val &= ~PRNG_LFSR_CFG_MASK;
+		val |= PRNG_LFSR_CFG_CLOCKS;
+		writel(val, rng->base + PRNG_LFSR_CFG);
+
+		val = readl_relaxed(rng->base + PRNG_CONFIG);
+		val |= PRNG_CONFIG_HW_ENABLE;
+		writel(val, rng->base + PRNG_CONFIG);
+	} else {
+		val = readl_relaxed(rng->base + PRNG_CONFIG);
+		val &= ~PRNG_CONFIG_HW_ENABLE;
+		writel(val, rng->base + PRNG_CONFIG);
+	}
+
+already_enabled:
+	clk_disable_unprepare(rng->clk);
+	return 0;
+}
+
+static int msm_rng_read(struct hwrng *hwrng, void *data, size_t max, bool wait)
+{
+	struct msm_rng *rng = to_msm_rng(hwrng);
+	size_t currsize = 0;
+	u32 *retdata = data;
+	size_t maxsize;
+	int ret;
+	u32 val;
+
+	/* calculate max size bytes to transfer back to caller */
+	maxsize = min_t(size_t, MAX_HW_FIFO_SIZE, max);
+
+	/* no room for word data */
+	if (maxsize < WORD_SZ)
+		return 0;
+
+	ret = clk_prepare_enable(rng->clk);
+	if (ret)
+		return ret;
+
+	/* read random data from hardware */
+	do {
+		val = readl_relaxed(rng->base + PRNG_STATUS);
+		if (!(val & PRNG_STATUS_DATA_AVAIL))
+			break;
+
+		val = readl_relaxed(rng->base + PRNG_DATA_OUT);
+		if (!val)
+			break;
+
+		*retdata++ = val;
+		currsize += WORD_SZ;
+
+		/* make sure we stay on 32bit boundary */
+		if ((maxsize - currsize) < WORD_SZ)
+			break;
+	} while (currsize < maxsize);
+
+	clk_disable_unprepare(rng->clk);
+
+	return currsize;
+}
+
+static int msm_rng_init(struct hwrng *hwrng)
+{
+	return msm_rng_enable(hwrng, 1);
+}
+
+static void msm_rng_cleanup(struct hwrng *hwrng)
+{
+	msm_rng_enable(hwrng, 0);
+}
+
+static int msm_rng_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	struct msm_rng *rng;
+	int ret;
+
+	rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
+	if (!rng)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, rng);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	rng->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(rng->base))
+		return PTR_ERR(rng->base);
+
+	rng->clk = devm_clk_get(&pdev->dev, "core");
+	if (IS_ERR(rng->clk))
+		return PTR_ERR(rng->clk);
+
+	rng->hwrng.name = KBUILD_MODNAME,
+	rng->hwrng.init = msm_rng_init,
+	rng->hwrng.cleanup = msm_rng_cleanup,
+	rng->hwrng.read = msm_rng_read,
+
+	ret = hwrng_register(&rng->hwrng);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to register hwrng\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int msm_rng_remove(struct platform_device *pdev)
+{
+	struct msm_rng *rng = platform_get_drvdata(pdev);
+
+	hwrng_unregister(&rng->hwrng);
+	return 0;
+}
+
+static const struct of_device_id msm_rng_of_match[] = {
+	{ .compatible = "qcom,prng", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, msm_rng_of_match);
+
+static struct platform_driver msm_rng_driver = {
+	.probe = msm_rng_probe,
+	.remove = msm_rng_remove,
+	.driver = {
+		.name = KBUILD_MODNAME,
+		.owner = THIS_MODULE,
+		.of_match_table = of_match_ptr(msm_rng_of_match),
+	}
+};
+module_platform_driver(msm_rng_driver);
+
+MODULE_ALIAS("platform:" KBUILD_MODNAME);
+MODULE_AUTHOR("The Linux Foundation");
+MODULE_DESCRIPTION("Qualcomm MSM random number generator driver");
+MODULE_LICENSE("GPL v2");