[PATCH 03/10] hwrng: stm32 - implement STM32MP13x support

Gatien Chevallier
2023-09-08T16:52:10Z

The RNG present on STM32MP13x platforms introduces a customizable
configuration and the conditional reset.

STM32 RNG configuration should best fit the requirements of the
platform. Therefore, put a platform-specific RNG configuration
field in the platform data. Default RNG configuration for STM32MP13
is the NIST certified configuration [1].

While there, fix and the RNG init sequence to support all RNG
versions.

[1] https://csrc.nist.gov/projects/cryptographic-module-validation-program/entropy-validations/certificate/53

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
---
drivers/char/hw_random/stm32-rng.c | 222 ++++++++++++++++++++---------
1 file changed, 158 insertions(+), 64 deletions(-)

diff --git a/drivers/char/hw_random/stm32-rng.c b/drivers/char/hw_random/stm32-rng.c
index d64d25d0fee8..54bd5807bbac 100644
--- a/drivers/char/hw_random/stm32-rng.c
+++ b/drivers/char/hw_random/stm32-rng.c
@@ -17,22 +17,43 @@
#include <linux/reset.h>
#include <linux/slab.h>

-#define RNG_CR 0x00
-#define RNG_CR_RNGEN BIT(2)
-#define RNG_CR_CED BIT(5)
-
-#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
+#define RNG_CR 0x00
+#define RNG_CR_RNGEN BIT(2)
+#define RNG_CR_CED BIT(5)
+#define RNG_CR_CONFIG1 GENMASK(11, 8)
+#define RNG_CR_NISTC BIT(12)
+#define RNG_CR_CONFIG2 GENMASK(15, 13)
+#define RNG_CR_CONFIG3 GENMASK(25, 20)
+#define RNG_CR_CONDRST BIT(30)
+#define RNG_CR_CONFLOCK BIT(31)
+#define RNG_CR_ENTROPY_SRC_MASK (RNG_CR_CONFIG1 | RNG_CR_NISTC | RNG_CR_CONFIG2 | RNG_CR_CONFIG3)
+#define RNG_CR_CONFIG_MASK (RNG_CR_ENTROPY_SRC_MASK | RNG_CR_CED)
+
+#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
+
+#define RNG_NSCR 0x0C
+#define RNG_NSCR_MASK GENMASK(17, 0)
+
+#define RNG_HTCR 0x10
+
+struct stm32_rng_data {
+ u32 cr;
+ u32 nscr;
+ u32 htcr;
+ bool has_cond_reset;
+};

struct stm32_rng_private {
struct hwrng rng;
void __iomem *base;
struct clk *clk;
struct reset_control *rst;
+ const struct stm32_rng_data *data;
bool ced;
};

@@ -87,32 +108,145 @@ static int stm32_rng_init(struct hwrng *rng)
struct stm32_rng_private *priv =
container_of(rng, struct stm32_rng_private, rng);
int err;
+ u32 reg;

err = clk_prepare_enable(priv->clk);
if (err)
return err;

- if (priv->ced)
- writel_relaxed(RNG_CR_RNGEN, priv->base + RNG_CR);
- else
- writel_relaxed(RNG_CR_RNGEN | RNG_CR_CED,
- priv->base + RNG_CR);
-
/* clear error indicators */
writel_relaxed(0, priv->base + RNG_SR);

+ reg = readl_relaxed(priv->base + RNG_CR);
+
+ /*
+ * Keep default RNG configuration if none was specified.
+ * 0 is an invalid value as it disables all entropy sources.
+ */
+ if (priv->data->has_cond_reset && priv->data->cr) {
+ reg &= ~RNG_CR_CONFIG_MASK;
+ reg |= RNG_CR_CONDRST | (priv->data->cr & RNG_CR_ENTROPY_SRC_MASK);
+ if (priv->ced)
+ reg &= ~RNG_CR_CED;
+ else
+ reg |= RNG_CR_CED;
+ writel_relaxed(reg, priv->base + RNG_CR);
+
+ /* Health tests and noise control registers */
+ writel_relaxed(priv->data->htcr, priv->base + RNG_HTCR);
+ writel_relaxed(priv->data->nscr & RNG_NSCR_MASK, priv->base + RNG_NSCR);
+
+ reg &= ~RNG_CR_CONDRST;
+ reg |= RNG_CR_RNGEN;
+ writel_relaxed(reg, priv->base + RNG_CR);
+
+ err = readl_relaxed_poll_timeout_atomic(priv->base + RNG_CR, reg,
+ (!(reg & RNG_CR_CONDRST)),
+ 10, 50000);
+ if (err) {
+ dev_err((struct device *)priv->rng.priv,
+ "%s: timeout %x!\n", __func__, reg);
+ return -EINVAL;
+ }
+ } else {
+ /* Handle all RNG versions by checking if conditional reset should be set */
+ if (priv->data->has_cond_reset)
+ reg |= RNG_CR_CONDRST;
+
+ if (priv->ced)
+ reg &= ~RNG_CR_CED;
+ else
+ reg |= RNG_CR_CED;
+
+ writel_relaxed(reg, priv->base + RNG_CR);
+
+ if (priv->data->has_cond_reset)
+ reg &= ~RNG_CR_CONDRST;
+
+ reg |= RNG_CR_RNGEN;
+
+ writel_relaxed(reg, priv->base + RNG_CR);
+ }
+
+ err = readl_relaxed_poll_timeout_atomic(priv->base + RNG_SR, reg,
+ reg & RNG_SR_DRDY,
+ 10, 100000);
+ if (err | (reg & ~RNG_SR_DRDY)) {
+ clk_disable_unprepare(priv->clk);
+ dev_err((struct device *)priv->rng.priv,
+ "%s: timeout:%x SR: %x!\n", __func__, err, reg);
+ return -EINVAL;
+ }
+
return 0;
}

-static void stm32_rng_cleanup(struct hwrng *rng)
+static int stm32_rng_remove(struct platform_device *ofdev)
{
- struct stm32_rng_private *priv =
- container_of(rng, struct stm32_rng_private, rng);
+ pm_runtime_disable(&ofdev->dev);
+
+ return 0;
+}
+
+#ifdef CONFIG_PM
+static int stm32_rng_runtime_suspend(struct device *dev)
+{
+ u32 reg;
+ struct stm32_rng_private *priv = dev_get_drvdata(dev);

- writel_relaxed(0, priv->base + RNG_CR);
+ reg = readl_relaxed(priv->base + RNG_CR);
+ reg &= ~RNG_CR_RNGEN;
+ writel_relaxed(reg, priv->base + RNG_CR);
clk_disable_unprepare(priv->clk);
+
+ return 0;
}

+static int stm32_rng_runtime_resume(struct device *dev)
+{
+ u32 reg;
+ struct stm32_rng_private *priv = dev_get_drvdata(dev);
+
+ clk_prepare_enable(priv->clk);
+ reg = readl_relaxed(priv->base + RNG_CR);
+ reg |= RNG_CR_RNGEN;
+ writel_relaxed(reg, priv->base + RNG_CR);
+
+ return 0;
+}
+#endif
+
+static const struct dev_pm_ops stm32_rng_pm_ops = {
+ SET_RUNTIME_PM_OPS(stm32_rng_runtime_suspend,
+ stm32_rng_runtime_resume, NULL)
+ SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
+ pm_runtime_force_resume)
+};
+
+static const struct stm32_rng_data stm32mp13_rng_data = {
+ .has_cond_reset = true,
+ .cr = 0x00F00D00,
+ .nscr = 0x2B5BB,
+ .htcr = 0x969D,
+};
+
+static const struct stm32_rng_data stm32_rng_data = {
+ .has_cond_reset = false,
+};
+
+static const struct of_device_id stm32_rng_match[] = {
+ {
+ .compatible = "st,stm32mp13-rng",
+ .data = &stm32mp13_rng_data,
+ },
+ {
+ .compatible = "st,stm32-rng",
+ .data = &stm32_rng_data,
+ },
+ {},
+};
+MODULE_DEVICE_TABLE(of, stm32_rng_match);
+
static int stm32_rng_probe(struct platform_device *ofdev)
{
struct device *dev = &ofdev->dev;
@@ -141,13 +275,14 @@ static int stm32_rng_probe(struct platform_device *ofdev)

priv->ced = of_property_read_bool(np, "clock-error-detect");

+ priv->data = of_device_get_match_data(dev);
+ if (!priv->data)
+ return -ENODEV;
+
dev_set_drvdata(dev, priv);

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;
priv->rng.quality = 900;
@@ -159,47 +294,6 @@ static int stm32_rng_probe(struct platform_device *ofdev)
return devm_hwrng_register(dev, &priv->rng);
}

-static int stm32_rng_remove(struct platform_device *ofdev)
-{
- pm_runtime_disable(&ofdev->dev);
-
- return 0;
-}
-
-#ifdef CONFIG_PM
-static int stm32_rng_runtime_suspend(struct device *dev)
-{
- struct stm32_rng_private *priv = dev_get_drvdata(dev);
-
- stm32_rng_cleanup(&priv->rng);
-
- return 0;
-}
-
-static int stm32_rng_runtime_resume(struct device *dev)
-{
- struct stm32_rng_private *priv = dev_get_drvdata(dev);
-
- return stm32_rng_init(&priv->rng);
-}
-#endif
-
-static const struct dev_pm_ops stm32_rng_pm_ops = {
- SET_RUNTIME_PM_OPS(stm32_rng_runtime_suspend,
- stm32_rng_runtime_resume, NULL)
- SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
- pm_runtime_force_resume)
-};
-
-
-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",
--
2.25.1