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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@linaro.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Daniel Thompson
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Herbert Xu
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Oct 14, 2015
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/* | ||
* 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. | ||
*/ | ||
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#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/pm_runtime.h> | ||
#include <linux/slab.h> | ||
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#define RNG_CR 0x00 | ||
#define RNG_CR_RNGEN BIT(2) | ||
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#define RNG_SR 0x04 | ||
#define RNG_SR_SEIS BIT(6) | ||
#define RNG_SR_CEIS BIT(5) | ||
#define RNG_SR_DRDY BIT(0) | ||
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#define RNG_DR 0x08 | ||
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/* | ||
* 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 iteration so the | ||
* timeout is enough to take us up to multi-GHz parts! | ||
*/ | ||
#define RNG_TIMEOUT 500 | ||
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struct stm32_rng_private { | ||
struct hwrng rng; | ||
void __iomem *base; | ||
struct clk *clk; | ||
}; | ||
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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 sr; | ||
int retval = 0; | ||
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pm_runtime_get_sync((struct device *) priv->rng.priv); | ||
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while (max > sizeof(u32)) { | ||
sr = readl_relaxed(priv->base + RNG_SR); | ||
if (!sr && wait) { | ||
unsigned int timeout = RNG_TIMEOUT; | ||
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do { | ||
cpu_relax(); | ||
sr = readl_relaxed(priv->base + RNG_SR); | ||
} while (!sr && --timeout); | ||
} | ||
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/* If error detected or data not ready... */ | ||
if (sr != RNG_SR_DRDY) | ||
break; | ||
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*(u32 *)data = readl_relaxed(priv->base + RNG_DR); | ||
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retval += sizeof(u32); | ||
data += sizeof(u32); | ||
max -= sizeof(u32); | ||
} | ||
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if (WARN_ONCE(sr & (RNG_SR_SEIS | RNG_SR_CEIS), | ||
"bad RNG status - %x\n", sr)) | ||
writel_relaxed(0, priv->base + RNG_SR); | ||
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pm_runtime_mark_last_busy((struct device *) priv->rng.priv); | ||
pm_runtime_put_sync_autosuspend((struct device *) priv->rng.priv); | ||
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return retval || !wait ? retval : -EIO; | ||
} | ||
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static int stm32_rng_init(struct hwrng *rng) | ||
{ | ||
struct stm32_rng_private *priv = | ||
container_of(rng, struct stm32_rng_private, rng); | ||
int err; | ||
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err = clk_prepare_enable(priv->clk); | ||
if (err) | ||
return err; | ||
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writel_relaxed(RNG_CR_RNGEN, priv->base + RNG_CR); | ||
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/* clear error indicators */ | ||
writel_relaxed(0, priv->base + RNG_SR); | ||
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return 0; | ||
} | ||
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static void stm32_rng_cleanup(struct hwrng *rng) | ||
{ | ||
struct stm32_rng_private *priv = | ||
container_of(rng, struct stm32_rng_private, rng); | ||
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writel_relaxed(0, priv->base + RNG_CR); | ||
clk_disable_unprepare(priv->clk); | ||
} | ||
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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; | ||
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priv = devm_kzalloc(dev, sizeof(struct stm32_rng_private), GFP_KERNEL); | ||
if (!priv) | ||
return -ENOMEM; | ||
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err = of_address_to_resource(np, 0, &res); | ||
if (err) | ||
return err; | ||
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priv->base = devm_ioremap_resource(dev, &res); | ||
if (IS_ERR(priv->base)) | ||
return PTR_ERR(priv->base); | ||
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priv->clk = devm_clk_get(&ofdev->dev, NULL); | ||
if (IS_ERR(priv->clk)) | ||
return PTR_ERR(priv->clk); | ||
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dev_set_drvdata(dev, priv); | ||
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priv->rng.name = dev_driver_string(dev), | ||
#ifndef CONFIG_PM | ||
priv->rng.init = stm32_rng_init, | ||
priv->rng.cleanup = stm32_rng_cleanup, | ||
#endif | ||
priv->rng.read = stm32_rng_read, | ||
priv->rng.priv = (unsigned long) dev; | ||
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pm_runtime_set_autosuspend_delay(dev, 100); | ||
pm_runtime_use_autosuspend(dev); | ||
pm_runtime_enable(dev); | ||
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return devm_hwrng_register(dev, &priv->rng); | ||
} | ||
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#ifdef CONFIG_PM | ||
static int stm32_rng_runtime_suspend(struct device *dev) | ||
{ | ||
struct stm32_rng_private *priv = dev_get_drvdata(pdev); | ||
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stm32_rng_cleanup(&priv->rng); | ||
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return 0; | ||
} | ||
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static int stm32_rng_runtime_resume(struct device *dev) | ||
{ | ||
struct stm32_rng_private *priv = dev_get_drvdata(pdev); | ||
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return stm32_rng_init(&priv->rng); | ||
} | ||
#endif | ||
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static UNIVERSAL_DEV_PM_OPS(stm32_rng_pm_ops, stm32_rng_runtime_suspend, | ||
stm32_rng_runtime_resume, NULL); | ||
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static const struct of_device_id stm32_rng_match[] = { | ||
{ | ||
.compatible = "st,stm32-rng", | ||
}, | ||
{}, | ||
}; | ||
MODULE_DEVICE_TABLE(of, stm32_rng_match); | ||
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static struct platform_driver stm32_rng_driver = { | ||
.driver = { | ||
.name = "stm32-rng", | ||
.pm = &stm32_rng_pm_ops, | ||
.of_match_table = stm32_rng_match, | ||
}, | ||
.probe = stm32_rng_probe, | ||
}; | ||
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module_platform_driver(stm32_rng_driver); | ||
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MODULE_LICENSE("GPL"); | ||
MODULE_AUTHOR("Daniel Thompson <daniel.thompson@linaro.org>"); | ||
MODULE_DESCRIPTION("STMicroelectronics STM32 RNG device driver"); |