[PATCH v10 2/6] hwrng: starfive - fix runtime PM and power teardown handling
From: lianfeng.ouyang
Date: Thu Oct 22 2026 - 22:14:33 EST
From: Lianfeng Ouyang <lianfeng.ouyang@xxxxxxxxxxxxxxxx>
The runtime PM bookkeeping of the driver does not match the hardware
state it leaves behind:
- probe enables the clocks and deasserts the reset, but then calls
pm_runtime_enable() without marking the device active. The first
pm_runtime_get_sync() in ->read() therefore runs the resume callback
and enables the clocks a second time, and the autosuspend only ever
drops that extra reference, so the clocks are never gated.
- the system sleep ops point at the runtime callbacks. When the device
is already runtime suspended, a system suspend gates the clocks a
second time.
- ->cleanup() asserts the reset and gates the clocks, but ->init()
never undoes that. Deselecting and reselecting the device through
rng_current reinitialises it with the clocks off. On remove, the
clocks taken in probe are only dropped if ->cleanup() happened to
run.
- ->init() and ->cleanup() access the registers without holding a
runtime PM reference.
Move the clock and reset handling into starfive_trng_power_on() and
starfive_trng_power_off(), which track what is currently enabled, and
tear the hardware down from a devm action so that every probe error
path and remove unwind it. Mark the device active before enabling
runtime PM with devm_pm_runtime_set_active_enabled() and let it
autosuspend from pm_runtime_idle(). Use DEFINE_RUNTIME_DEV_PM_OPS() so
that system sleep goes through pm_runtime_force_suspend() and
pm_runtime_force_resume(). Take a runtime PM reference in ->init() and
->cleanup(), and make ->cleanup() only quiesce the hardware; runtime PM
and the devm action take care of powering it down.
Fixes: 9b2b61126a06 ("hwrng: starfive - Add runtime pm ops")
Fixes: c388f458bc34 ("hwrng: starfive - Add TRNG driver for StarFive SoC")
Signed-off-by: Lianfeng Ouyang <lianfeng.ouyang@xxxxxxxxxxxxxxxx>
---
drivers/char/hw_random/jh7110-trng.c | 150 ++++++++++++++++++---------
1 file changed, 103 insertions(+), 47 deletions(-)
diff --git a/drivers/char/hw_random/jh7110-trng.c b/drivers/char/hw_random/jh7110-trng.c
index 61eb4db7ac01..17932cc6d7aa 100644
--- a/drivers/char/hw_random/jh7110-trng.c
+++ b/drivers/char/hw_random/jh7110-trng.c
@@ -104,6 +104,8 @@ struct starfive_trng {
u32 mode;
u32 mission;
u32 reseed;
+ bool clk_on;
+ bool rst_deassert;
/* protects against concurrent write to ctrl register */
spinlock_t write_lock;
};
@@ -138,6 +140,60 @@ static inline void starfive_trng_irq_mask_clear(struct starfive_trng *trng)
writel(data, trng->base + STARFIVE_ISTAT);
}
+static int starfive_trng_power_on(struct starfive_trng *trng)
+{
+ int ret;
+
+ if (!trng->clk_on) {
+ ret = clk_prepare_enable(trng->hclk);
+ if (ret)
+ goto err_hclk;
+
+ ret = clk_prepare_enable(trng->ahb);
+ if (ret)
+ goto err_ahb;
+
+ trng->clk_on = true;
+ }
+
+ if (!trng->rst_deassert) {
+ ret = reset_control_deassert(trng->rst);
+ if (ret)
+ goto err_rst;
+
+ trng->rst_deassert = true;
+ }
+
+ return 0;
+
+err_rst:
+ clk_disable_unprepare(trng->ahb);
+err_ahb:
+ clk_disable_unprepare(trng->hclk);
+ trng->clk_on = false;
+err_hclk:
+ return ret;
+}
+
+static void starfive_trng_power_off(struct starfive_trng *trng, bool assert_rst)
+{
+ if (assert_rst && trng->rst_deassert) {
+ reset_control_assert(trng->rst);
+ trng->rst_deassert = false;
+ }
+
+ if (trng->clk_on) {
+ clk_disable_unprepare(trng->ahb);
+ clk_disable_unprepare(trng->hclk);
+ trng->clk_on = false;
+ }
+}
+
+static void starfive_trng_power_off_action(void *data)
+{
+ starfive_trng_power_off(data, true);
+}
+
static int starfive_trng_cmd(struct starfive_trng *trng, u32 cmd, bool wait)
{
int wait_time = 1000;
@@ -174,6 +230,13 @@ static int starfive_trng_init(struct hwrng *rng)
{
struct starfive_trng *trng = to_trng(rng);
u32 mode, intr = 0;
+ int ret;
+
+ ret = pm_runtime_resume_and_get(trng->dev);
+ if (ret < 0) {
+ dev_err(trng->dev, "Failed to wake device for init: %d\n", ret);
+ return ret;
+ }
/* setup Auto Request/Age register */
writel(autoage, trng->base + STARFIVE_AUTO_AGE);
@@ -201,7 +264,11 @@ static int starfive_trng_init(struct hwrng *rng)
writel(mode, trng->base + STARFIVE_MODE);
- return starfive_trng_cmd(trng, STARFIVE_CTRL_EXEC_RANDRESEED, 1);
+ ret = starfive_trng_cmd(trng, STARFIVE_CTRL_EXEC_RANDRESEED, 1);
+
+ pm_runtime_put_autosuspend(trng->dev);
+
+ return ret;
}
static irqreturn_t starfive_trng_irq(int irq, void *priv)
@@ -234,12 +301,17 @@ static irqreturn_t starfive_trng_irq(int irq, void *priv)
static void starfive_trng_cleanup(struct hwrng *rng)
{
struct starfive_trng *trng = to_trng(rng);
+ int ret;
+
+ ret = pm_runtime_resume_and_get(trng->dev);
+ if (ret < 0) {
+ dev_err(trng->dev, "Failed to wake device for cleanup: %d\n", ret);
+ return;
+ }
- writel(0, trng->base + STARFIVE_CTRL);
+ writel(STARFIVE_CTRL_EXEC_NOP, trng->base + STARFIVE_CTRL);
- reset_control_assert(trng->rst);
- clk_disable_unprepare(trng->hclk);
- clk_disable_unprepare(trng->ahb);
+ pm_runtime_put_sync_suspend(trng->dev);
}
static int starfive_trng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
@@ -247,7 +319,11 @@ static int starfive_trng_read(struct hwrng *rng, void *buf, size_t max, bool wai
struct starfive_trng *trng = to_trng(rng);
int ret;
- pm_runtime_get_sync(trng->dev);
+ ret = pm_runtime_resume_and_get(trng->dev);
+ if (ret < 0) {
+ dev_warn_ratelimited(trng->dev, "Failed to wake device for read: %d\n", ret);
+ return ret;
+ }
if (trng->mode == PRNG_256BIT)
max = min_t(size_t, max, (STARFIVE_RAND_LEN * 8));
@@ -270,7 +346,7 @@ static int starfive_trng_read(struct hwrng *rng, void *buf, size_t max, bool wai
ret = max;
out_put:
- pm_runtime_put_sync_autosuspend(trng->dev);
+ pm_runtime_put_autosuspend(trng->dev);
return ret;
}
@@ -320,17 +396,13 @@ static int starfive_trng_probe(struct platform_device *pdev)
return dev_err_probe(&pdev->dev, PTR_ERR(trng->rst),
"Error getting hardware reset line\n");
- ret = clk_prepare_enable(trng->hclk);
- if (ret)
- return ret;
-
- ret = clk_prepare_enable(trng->ahb);
+ ret = starfive_trng_power_on(trng);
if (ret)
- goto disable_hclk;
+ return dev_err_probe(&pdev->dev, ret, "Failed to power on\n");
- ret = reset_control_deassert(trng->rst);
+ ret = devm_add_action_or_reset(&pdev->dev, starfive_trng_power_off_action, trng);
if (ret)
- goto disable_ahb;
+ return ret;
trng->rng.name = dev_driver_string(&pdev->dev);
trng->rng.init = starfive_trng_init;
@@ -343,71 +415,55 @@ static int starfive_trng_probe(struct platform_device *pdev)
pm_runtime_use_autosuspend(&pdev->dev);
pm_runtime_set_autosuspend_delay(&pdev->dev, 100);
- pm_runtime_enable(&pdev->dev);
+
+ ret = devm_pm_runtime_set_active_enabled(&pdev->dev);
+ if (ret)
+ return dev_err_probe(&pdev->dev, ret, "Failed to enable runtime PM\n");
ret = devm_hwrng_register(&pdev->dev, &trng->rng);
- if (ret) {
- pm_runtime_disable(&pdev->dev);
+ if (ret)
+ return dev_err_probe(&pdev->dev, ret, "Failed to register hwrng\n");
- reset_control_assert(trng->rst);
- ret = dev_err_probe(&pdev->dev, ret, "Failed to register hwrng\n");
- goto disable_ahb;
- }
+ pm_runtime_idle(&pdev->dev);
return 0;
-
-disable_ahb:
- clk_disable_unprepare(trng->ahb);
-disable_hclk:
- clk_disable_unprepare(trng->hclk);
-
- return ret;
}
-static int __maybe_unused starfive_trng_suspend(struct device *dev)
+static int starfive_trng_suspend(struct device *dev)
{
struct starfive_trng *trng = dev_get_drvdata(dev);
- clk_disable_unprepare(trng->hclk);
- clk_disable_unprepare(trng->ahb);
+ starfive_trng_power_off(trng, false);
return 0;
}
-static int __maybe_unused starfive_trng_resume(struct device *dev)
+static int starfive_trng_resume(struct device *dev)
{
struct starfive_trng *trng = dev_get_drvdata(dev);
int ret;
- ret = clk_prepare_enable(trng->hclk);
- if (ret)
- return ret;
-
- ret = clk_prepare_enable(trng->ahb);
+ ret = starfive_trng_power_on(trng);
if (ret)
- clk_disable_unprepare(trng->hclk);
+ dev_err(dev, "Failed to power on: %d\n", ret);
return ret;
}
-static const struct dev_pm_ops starfive_trng_pm_ops = {
- SET_SYSTEM_SLEEP_PM_OPS(starfive_trng_suspend,
- starfive_trng_resume)
- SET_RUNTIME_PM_OPS(starfive_trng_suspend,
- starfive_trng_resume, NULL)
-};
-
static const struct of_device_id trng_dt_ids[] __maybe_unused = {
{ .compatible = "starfive,jh7110-trng" },
{ }
};
MODULE_DEVICE_TABLE(of, trng_dt_ids);
+static DEFINE_RUNTIME_DEV_PM_OPS(starfive_trng_pm_ops,
+ starfive_trng_suspend, starfive_trng_resume, NULL);
+
static struct platform_driver starfive_trng_driver = {
.probe = starfive_trng_probe,
.driver = {
.name = "jh7110-trng",
- .pm = &starfive_trng_pm_ops,
+ .pm = pm_ptr(&starfive_trng_pm_ops),
.of_match_table = of_match_ptr(trng_dt_ids),
},
};
--
2.43.0