[PATCH 4/6] hwrng: st: Add support for ST's HW Random Number Generator

Lee Jones
2015-09-11T20:11:34Z

Signed-off-by: Pankaj Dev <pankaj.dev@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
drivers/char/hw_random/Kconfig | 10 +++
drivers/char/hw_random/Makefile | 1 +
drivers/char/hw_random/st-rng.c | 142 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 153 insertions(+)
create mode 100644 drivers/char/hw_random/st-rng.c

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index f48cf11..bb6cb77 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/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
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 055bb01..8bcfb45 100644
--- a/drivers/char/hw_random/Makefile
+++ b/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
diff --git a/drivers/char/hw_random/st-rng.c b/drivers/char/hw_random/st-rng.c
new file mode 100644
index 0000000..717a831
--- /dev/null
+++ b/drivers/char/hw_random/st-rng.c
@@ -0,0 +1,142 @@
+/*
+ * 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 - 2; /* 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 (!clk)
+ return -EINVAL;
+
+ clk_prepare_enable(clk);
+
+ 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");
--
1.9.1