hwrng: st - Add support for ST's HW Random Number Generator

Signed-off-by: Pankaj Dev <pankaj.dev@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Kieran Bingham <kieranbingham@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/Kconfig

@@ -346,6 +346,16 @@ config HW_RANDOM_MSM
 
 	  If unsure, say Y.
 
+config HW_RANDOM_ST
+	tristate "ST Microelectronics HW Random Number Generator support"
+	depends on HW_RANDOM && ARCH_STI
+	---help---
+	  This driver provides kernel-side support for the Random Number
+	  Generator hardware found on STi series of SoCs.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called st-rng.
+
 config HW_RANDOM_XGENE
 	tristate "APM X-Gene True Random Number Generator (TRNG) support"
 	depends on HW_RANDOM && ARCH_XGENE

drivers/char/hw_random/Makefile

@@ -30,4 +30,5 @@ obj-$(CONFIG_HW_RANDOM_TPM) += tpm-rng.o
 obj-$(CONFIG_HW_RANDOM_BCM2835) += bcm2835-rng.o
 obj-$(CONFIG_HW_RANDOM_IPROC_RNG200) += iproc-rng200.o
 obj-$(CONFIG_HW_RANDOM_MSM) += msm-rng.o
+obj-$(CONFIG_HW_RANDOM_ST) += st-rng.o
 obj-$(CONFIG_HW_RANDOM_XGENE) += xgene-rng.o

drivers/char/hw_random/st-rng.c

+/*
+ * ST Random Number Generator Driver ST's Platforms
+ *
+ * Author: Pankaj Dev: <pankaj.dev@st.com>
+ *         Lee Jones <lee.jones@linaro.org>
+ *
+ * Copyright (C) 2015 STMicroelectronics (R&D) Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+/* Registers */
+#define ST_RNG_STATUS_REG		0x20
+#define ST_RNG_DATA_REG			0x24
+
+/* Registers fields */
+#define ST_RNG_STATUS_BAD_SEQUENCE	BIT(0)
+#define ST_RNG_STATUS_BAD_ALTERNANCE	BIT(1)
+#define ST_RNG_STATUS_FIFO_FULL		BIT(5)
+
+#define ST_RNG_FIFO_SIZE		8
+#define ST_RNG_SAMPLE_SIZE		2 /* 2 Byte (16bit) samples */
+
+/* Samples are available every 0.667us, which we round to 1us */
+#define ST_RNG_FILL_FIFO_TIMEOUT   (1 * (ST_RNG_FIFO_SIZE / ST_RNG_SAMPLE_SIZE))
+
+struct st_rng_data {
+	void __iomem	*base;
+	struct clk	*clk;
+	struct hwrng	ops;
+};
+
+static int st_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+	struct st_rng_data *ddata = (struct st_rng_data *)rng->priv;
+	u32 status;
+	int i;
+
+	if (max < sizeof(u16))
+		return -EINVAL;
+
+	/* Wait until FIFO is full - max 4uS*/
+	for (i = 0; i < ST_RNG_FILL_FIFO_TIMEOUT; i++) {
+		status = readl_relaxed(ddata->base + ST_RNG_STATUS_REG);
+		if (status & ST_RNG_STATUS_FIFO_FULL)
+			break;
+		udelay(1);
+	}
+
+	if (i == ST_RNG_FILL_FIFO_TIMEOUT)
+		return 0;
+
+	for (i = 0; i < ST_RNG_FIFO_SIZE && i < max; i += 2)
+		*(u16 *)(data + i) =
+			readl_relaxed(ddata->base + ST_RNG_DATA_REG);
+
+	return i;	/* No of bytes read */
+}
+
+static int st_rng_probe(struct platform_device *pdev)
+{
+	struct st_rng_data *ddata;
+	struct resource *res;
+	struct clk *clk;
+	void __iomem *base;
+	int ret;
+
+	ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
+	if (!ddata)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	ret = clk_prepare_enable(clk);
+	if (ret)
+		return ret;
+
+	ddata->ops.priv	= (unsigned long)ddata;
+	ddata->ops.read	= st_rng_read;
+	ddata->ops.name	= pdev->name;
+	ddata->base	= base;
+	ddata->clk	= clk;
+
+	dev_set_drvdata(&pdev->dev, ddata);
+
+	ret = hwrng_register(&ddata->ops);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to register HW RNG\n");
+		return ret;
+	}
+
+	dev_info(&pdev->dev, "Successfully registered HW RNG\n");
+
+	return 0;
+}
+
+static int st_rng_remove(struct platform_device *pdev)
+{
+	struct st_rng_data *ddata = dev_get_drvdata(&pdev->dev);
+
+	hwrng_unregister(&ddata->ops);
+
+	clk_disable_unprepare(ddata->clk);
+
+	return 0;
+}
+
+static const struct of_device_id st_rng_match[] = {
+	{ .compatible = "st,rng" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, st_rng_match);
+
+static struct platform_driver st_rng_driver = {
+	.driver = {
+		.name = "st-hwrandom",
+		.of_match_table = of_match_ptr(st_rng_match),
+	},
+	.probe = st_rng_probe,
+	.remove = st_rng_remove
+};
+
+module_platform_driver(st_rng_driver);
+
+MODULE_AUTHOR("Pankaj Dev <pankaj.dev@st.com>");
+MODULE_LICENSE("GPL v2");