[PATCH 09/10] hwrng: stm32 - rework power management sequences

Gatien Chevallier
2023-09-08T16:54:59Z

Implement stm32_rng_suspend()/stm32_rng_resume() low-power APIs
called when the hardware block context will be lost.

There is no need to save the RNG_CR register in
stm32_rng_runtime_suspend() as the context is not lost. Therefore,
only enable/disable the RNG in the runtime sequences.

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
---
drivers/char/hw_random/stm32-rng.c | 100 +++++++++++++++++++++++++++--
1 file changed, 93 insertions(+), 7 deletions(-)

diff --git a/drivers/char/hw_random/stm32-rng.c b/drivers/char/hw_random/stm32-rng.c
index 0243b889ac54..3ac6712324c7 100644
--- a/drivers/char/hw_random/stm32-rng.c
+++ b/drivers/char/hw_random/stm32-rng.c
@@ -55,11 +55,25 @@ struct stm32_rng_data {
bool has_cond_reset;
};

+/**
+ * struct stm32_rng_config - RNG configuration data
+ *
+ * @cr: RNG configuration. 0 means default hardware RNG configuration
+ * @nscr: Noise sources control configuration.
+ * @htcr: Health tests configuration.
+ */
+struct stm32_rng_config {
+ u32 cr;
+ u32 nscr;
+ u32 htcr;
+};
+
struct stm32_rng_private {
struct hwrng rng;
void __iomem *base;
struct clk *clk;
struct reset_control *rst;
+ struct stm32_rng_config pm_conf;
const struct stm32_rng_data *data;
bool ced;
bool lock_conf;
@@ -355,11 +369,10 @@ static int stm32_rng_remove(struct platform_device *ofdev)
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);
+ u32 reg;

reg = readl_relaxed(priv->base + RNG_CR);
reg &= ~RNG_CR_RNGEN;
@@ -369,25 +382,98 @@ static int stm32_rng_runtime_suspend(struct device *dev)
return 0;
}

+static int __maybe_unused stm32_rng_suspend(struct device *dev)
+{
+ struct stm32_rng_private *priv = dev_get_drvdata(dev);
+
+ if (priv->data->has_cond_reset) {
+ priv->pm_conf.nscr = readl_relaxed(priv->base + RNG_NSCR);
+ priv->pm_conf.htcr = readl_relaxed(priv->base + RNG_HTCR);
+ }
+
+ /* Do not save that RNG is enabled as it will be handled at resume */
+ priv->pm_conf.cr = readl_relaxed(priv->base + RNG_CR) & ~RNG_CR_RNGEN;
+
+ writel_relaxed(priv->pm_conf.cr, 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);
+ int err;
+ u32 reg;
+
+ err = clk_prepare_enable(priv->clk);
+ if (err)
+ return err;
+
+ /* Clean error indications */
+ writel_relaxed(0, priv->base + RNG_SR);

- 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 int __maybe_unused stm32_rng_resume(struct device *dev)
+{
+ struct stm32_rng_private *priv = dev_get_drvdata(dev);
+ int err;
+ u32 reg;
+
+ err = clk_prepare_enable(priv->clk);
+ if (err)
+ return err;
+
+ /* Clean error indications */
+ writel_relaxed(0, priv->base + RNG_SR);
+
+ if (priv->data->has_cond_reset) {
+ /*
+ * Correct configuration in bits [29:4] must be set in the same
+ * access that set RNG_CR_CONDRST bit. Else config setting is
+ * not taken into account. CONFIGLOCK bit must also be unset but
+ * it is not handled at the moment.
+ */
+ writel_relaxed(priv->pm_conf.cr | RNG_CR_CONDRST, priv->base + RNG_CR);
+
+ writel_relaxed(priv->pm_conf.nscr, priv->base + RNG_NSCR);
+ writel_relaxed(priv->pm_conf.htcr, priv->base + RNG_HTCR);
+
+ reg = readl_relaxed(priv->base + RNG_CR);
+ reg |= RNG_CR_RNGEN;
+ reg &= ~RNG_CR_CONDRST;
+ writel_relaxed(reg, priv->base + RNG_CR);
+
+ err = readl_relaxed_poll_timeout_atomic(priv->base + RNG_CR, reg,
+ reg & ~RNG_CR_CONDRST, 10, 100000);
+
+ if (err) {
+ clk_disable_unprepare(priv->clk);
+ dev_err((struct device *)priv->rng.priv,
+ "%s: timeout:%x CR: %x!\n", __func__, err, reg);
+ return -EINVAL;
+ }
+ } else {
+ reg = priv->pm_conf.cr;
+ reg |= RNG_CR_RNGEN;
+ writel_relaxed(reg, priv->base + RNG_CR);
+ }
+
+ return 0;
+}

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)
+ SET_SYSTEM_SLEEP_PM_OPS(stm32_rng_suspend,
+ stm32_rng_resume)
};

static const struct stm32_rng_data stm32mp13_rng_data = {
--
2.25.1