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Message-Id: <1443904519-24012-3-git-send-email-daniel.thompson@linaro.org>
Date: Sat, 3 Oct 2015 21:35:18 +0100
From: Daniel Thompson <daniel.thompson@...aro.org>
To: Matt Mackall <mpm@...enic.com>,
Herbert Xu <herbert@...dor.apana.org.au>
Cc: Daniel Thompson <daniel.thompson@...aro.org>,
devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
patches@...aro.org, linaro-kernel@...ts.linaro.org,
Maxime Coquelin <mcoquelin.stm32@...il.com>,
Rob Herring <robh+dt@...nel.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>
Subject: [PATCH 2/3] hwrng: stm32 - add support for STM32 HW RNG
Add support for STMicroelectronics STM32 random number generator.
The config value defaults to N, reflecting the fact that STM32 is a
very low resource microcontroller platform and unlikely to be targeted
by any "grown up" defconfigs.
Signed-off-by: Daniel Thompson <daniel.thompson@...aro.org>
---
drivers/char/hw_random/Kconfig | 12 +++
drivers/char/hw_random/Makefile | 1 +
drivers/char/hw_random/stm32-rng.c | 192 +++++++++++++++++++++++++++++++++++++
3 files changed, 205 insertions(+)
create mode 100644 drivers/char/hw_random/stm32-rng.c
diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index f48cf11c655e..7930cc9b719c 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -359,6 +359,18 @@ config HW_RANDOM_XGENE
If unsure, say Y.
+config HW_RANDOM_STM32
+ tristate "STMicroelectronics STM32 random number generator"
+ depends on HW_RANDOM && (ARCH_STM32 || COMPILE_TEST)
+ help
+ This driver provides kernel-side support for the Random Number
+ Generator hardware found on STM32 microcontrollers.
+
+ To compile this driver as a module, choose M here: the
+ module will be called stm32-rng.
+
+ If unsure, say N.
+
endif # HW_RANDOM
config UML_RANDOM
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 055bb01510ad..8b49c0f7abb1 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -31,3 +31,4 @@ 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_XGENE) += xgene-rng.o
+obj-$(CONFIG_HW_RANDOM_STM32) += stm32-rng.o
diff --git a/drivers/char/hw_random/stm32-rng.c b/drivers/char/hw_random/stm32-rng.c
new file mode 100644
index 000000000000..37dfa5fca105
--- /dev/null
+++ b/drivers/char/hw_random/stm32-rng.c
@@ -0,0 +1,192 @@
+/*
+ * Copyright (c) 2015, Daniel Thompson
+ *
+ * This file 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 file 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/delay.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+#include <linux/slab.h>
+
+#define RNG_CR 0x00
+#define RNG_CR_RNGEN BIT(2)
+
+#define RNG_SR 0x04
+#define RNG_SR_SEIS BIT(6)
+#define RNG_SR_CEIS BIT(5)
+#define RNG_SR_DRDY BIT(0)
+
+#define RNG_DR 0x08
+
+/*
+ * It takes 40 cycles @ 48MHz to generate each random number (e.g. <1us).
+ * At the time of writing STM32 parts max out at ~200MHz meaning a timeout
+ * of 500 leaves us a very comfortable margin for error. The loop to which
+ * the timeout applies takes at least 4 instructions per cycle so the
+ * timeout is enough to take us up to multi-GHz parts!
+ */
+#define RNG_TIMEOUT 500
+
+struct stm32_rng_private {
+ struct hwrng rng;
+ void __iomem *base;
+ struct clk *clk;
+};
+
+static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+ struct stm32_rng_private *priv =
+ container_of(rng, struct stm32_rng_private, rng);
+ u32 cr, sr;
+ int retval = 0;
+
+ /* enable random number generation */
+ clk_enable(priv->clk);
+ cr = readl(priv->base + RNG_CR);
+ writel(cr | RNG_CR_RNGEN, priv->base + RNG_CR);
+
+ while (max > sizeof(u32)) {
+ sr = readl(priv->base + RNG_SR);
+ if (!sr && wait) {
+ unsigned int timeout = RNG_TIMEOUT;
+
+ do {
+ cpu_relax();
+ sr = readl(priv->base + RNG_SR);
+ } while (!sr && --timeout);
+ }
+
+ /* Has h/ware error dection been triggered? */
+ if (WARN_ON(sr & (RNG_SR_SEIS | RNG_SR_CEIS)))
+ break;
+
+ /* No data ready... */
+ if (!sr)
+ break;
+
+ *(u32 *)data = readl(priv->base + RNG_DR);
+
+ retval += sizeof(u32);
+ data += sizeof(u32);
+ max -= sizeof(u32);
+ }
+
+ /* disable the generator */
+ writel(cr, priv->base + RNG_CR);
+ clk_disable(priv->clk);
+
+ return retval || !wait ? retval : -EIO;
+}
+
+static int stm32_rng_init(struct hwrng *rng)
+{
+ struct stm32_rng_private *priv =
+ container_of(rng, struct stm32_rng_private, rng);
+ int err;
+ u32 sr;
+
+ err = clk_prepare(priv->clk);
+ if (err)
+ return err;
+
+ /* clear error indicators */
+ sr = readl(priv->base + RNG_SR);
+ sr &= ~(RNG_SR_SEIS | RNG_SR_CEIS);
+ writel(sr, priv->base + RNG_SR);
+
+ return 0;
+}
+
+static void stm32_rng_cleanup(struct hwrng *rng)
+{
+ struct stm32_rng_private *priv =
+ container_of(rng, struct stm32_rng_private, rng);
+
+ clk_unprepare(priv->clk);
+}
+
+static int stm32_rng_remove(struct platform_device *ofdev)
+{
+ struct device *dev = &ofdev->dev;
+ struct stm32_rng_private *priv = dev_get_drvdata(dev);
+
+ hwrng_unregister(&priv->rng);
+
+ return 0;
+}
+
+static int stm32_rng_probe(struct platform_device *ofdev)
+{
+ struct device *dev = &ofdev->dev;
+ struct device_node *np = ofdev->dev.of_node;
+ struct stm32_rng_private *priv;
+ struct resource res;
+ int err;
+
+ priv = devm_kzalloc(dev, sizeof(struct stm32_rng_private), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ err = of_address_to_resource(np, 0, &res);
+ if (err)
+ return err;
+
+ priv->base = devm_ioremap_resource(dev, &res);
+ if (IS_ERR(priv->base))
+ return PTR_ERR(priv->base);
+
+ priv->clk = devm_clk_get(&ofdev->dev, NULL);
+ if (IS_ERR(priv->clk))
+ return PTR_ERR(priv->clk);
+
+ dev_set_drvdata(dev, priv);
+
+ priv->rng.name = dev_driver_string(dev),
+ priv->rng.init = stm32_rng_init,
+ priv->rng.cleanup = stm32_rng_cleanup,
+ priv->rng.read = stm32_rng_read,
+ priv->rng.priv = (unsigned long) dev;
+
+ err = hwrng_register(&priv->rng);
+ if (err)
+ return err;
+
+ return 0;
+}
+
+static const struct of_device_id stm32_rng_match[] = {
+ {
+ .compatible = "st,stm32-rng",
+ },
+ {},
+};
+MODULE_DEVICE_TABLE(of, stm32_rng_match);
+
+static struct platform_driver stm32_rng_driver = {
+ .driver = {
+ .name = "stm32_rng",
+ .of_match_table = stm32_rng_match,
+ },
+ .probe = stm32_rng_probe,
+ .remove = stm32_rng_remove,
+};
+
+module_platform_driver(stm32_rng_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Daniel Thompson <daniel.thompson@...aro.org>");
+MODULE_DESCRIPTION("STMicroelectronics STM32 RNG device driver");
--
2.4.3
--
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