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@linaro.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@linaro.org"); +MODULE_DESCRIPTION("STMicroelectronics STM32 RNG device driver");