[PATCH v8 2/2] hwrng: starfive: rework clk/reset teardown order for JHB100

["lianfeng.ouyang" <lianfeng.ouyang@starfivetech.com>]

From: Lianfeng Ouyang <lianfeng.ouyang@starfivetech.com>

Rework the StarFive TRNG driver to address hardware-specific requirements
  for JHB100 SoC. To avoid reset-domain crossing glitches, the driver now
  ensures clocks are gated before asserting reset during teardown for
  JHB100, while JH7110 retains the original reset-first sequence.

Add per-compatible match data (struct starfive_trng_data) describing the
  clock/reset teardown order, a new "starfive,jhb100-trng" compatible, and
  select the ordering from it.

Fix the runtime-PM get/put balancing across the init/read/reseed/cleanup
  paths, manage PM and the clk/reset teardown via devm so all error paths
  unwind correctly, run the SEU-triggered reseed from a workqueue instead
  of hard IRQ, and serialise the command sequences with a mutex.

Signed-off-by: Lianfeng Ouyang <lianfeng.ouyang@starfivetech.com>
---
 MAINTAINERS                          |   2 +-
 drivers/char/hw_random/jh7110-trng.c | 297 +++++++++++++++++++++------
 2 files changed, 239 insertions(+), 60 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index 6d998ed051a8..5211aa88048f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -26239,7 +26239,7 @@ F:	Documentation/devicetree/bindings/perf/starfive,jh8100-starlink-pmu.yaml
 F:	drivers/perf/starfive_starlink_pmu.c
 
 STARFIVE TRNG DRIVER
-M:	Jia Jie Ho <jiajie.ho@starfivetech.com>
+M:	Lianfeng Ouyang <lianfeng.ouyang@starfivetech.com>
 S:	Supported
 F:	Documentation/devicetree/bindings/rng/starfive*
 F:	drivers/char/hw_random/jh7110-trng.c
diff --git a/drivers/char/hw_random/jh7110-trng.c b/drivers/char/hw_random/jh7110-trng.c
index aee12caab578..ecc7d5bd7bf5 100644
--- a/drivers/char/hw_random/jh7110-trng.c
+++ b/drivers/char/hw_random/jh7110-trng.c
@@ -92,22 +92,44 @@ enum mode {
 	PRNG_256BIT,
 };
 
+/*
+ * For JHB100, assert reset after disabling clocks to avoid
+ * reset-domain crossing (RDC) induced glitches that can affect
+ * downstream IPs.
+ */
+enum seq_rst_clk {
+	SEQ_RST_FIRST,
+	SEQ_CLK_FIRST,
+};
+
+struct starfive_trng_data {
+	enum seq_rst_clk	seq_rst_clk;
+};
+
 struct starfive_trng {
 	struct device		*dev;
 	void __iomem		*base;
+	int			irq;
 	struct clk		*hclk;
 	struct clk		*ahb;
 	struct reset_control	*rst;
 	struct hwrng		rng;
 	struct completion	random_done;
 	struct completion	reseed_done;
+	struct work_struct	work;
+	const struct starfive_trng_data *data;
 	u32			mode;
+	u32			cleanup;
 	u32			mission;
 	u32			reseed;
-	/* protects against concurrent write to ctrl register */
-	spinlock_t		write_lock;
+	struct mutex		lock; /* protect trng cmd seq */
 };
 
+static inline struct starfive_trng *work_to_trng(struct work_struct *work)
+{
+	return container_of(work, struct starfive_trng, work);
+}
+
 static u16 autoreq;
 module_param(autoreq, ushort, 0);
 MODULE_PARM_DESC(autoreq, "Auto-reseeding after random number requests by host reaches specified counter:\n"
@@ -130,7 +152,7 @@ static inline int starfive_trng_wait_idle(struct starfive_trng *trng)
 					  10, 100000);
 }
 
-static inline void starfive_trng_irq_mask_clear(struct starfive_trng *trng)
+static inline void starfive_trng_irq_clear(struct starfive_trng *trng)
 {
 	/* clear register: ISTAT */
 	u32 data = readl(trng->base + STARFIVE_ISTAT);
@@ -138,6 +160,28 @@ static inline void starfive_trng_irq_mask_clear(struct starfive_trng *trng)
 	writel(data, trng->base + STARFIVE_ISTAT);
 }
 
+static void starfive_trng_release(void *data)
+{
+	struct starfive_trng *trng = data;
+
+	if (!pm_runtime_status_suspended(trng->dev)) {
+		writel(0, trng->base + STARFIVE_IE);
+		starfive_trng_irq_clear(trng);
+
+		if (trng->irq >= 0)
+			synchronize_irq(trng->irq);
+
+		if (trng->data->seq_rst_clk == SEQ_RST_FIRST)
+			reset_control_assert(trng->rst);
+
+		clk_disable_unprepare(trng->ahb);
+		clk_disable_unprepare(trng->hclk);
+
+		if (trng->data->seq_rst_clk == SEQ_CLK_FIRST)
+			reset_control_assert(trng->rst);
+	}
+}
+
 static int starfive_trng_cmd(struct starfive_trng *trng, u32 cmd, bool wait)
 {
 	int wait_time = 1000;
@@ -149,17 +193,13 @@ static int starfive_trng_cmd(struct starfive_trng *trng, u32 cmd, bool wait)
 	switch (cmd) {
 	case STARFIVE_CTRL_GENE_RANDNUM:
 		reinit_completion(&trng->random_done);
-		spin_lock_irq(&trng->write_lock);
 		writel(cmd, trng->base + STARFIVE_CTRL);
-		spin_unlock_irq(&trng->write_lock);
 		if (!wait_for_completion_timeout(&trng->random_done, usecs_to_jiffies(wait_time)))
 			return -ETIMEDOUT;
 		break;
 	case STARFIVE_CTRL_EXEC_RANDRESEED:
 		reinit_completion(&trng->reseed_done);
-		spin_lock_irq(&trng->write_lock);
 		writel(cmd, trng->base + STARFIVE_CTRL);
-		spin_unlock_irq(&trng->write_lock);
 		if (!wait_for_completion_timeout(&trng->reseed_done, usecs_to_jiffies(wait_time)))
 			return -ETIMEDOUT;
 		break;
@@ -174,13 +214,24 @@ 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_warn(trng->dev, "Failed to wake device for init: %d\n", ret);
+		return ret;
+	}
+
+	mutex_lock(&trng->lock);
+
+	WRITE_ONCE(trng->cleanup, 0);
 
 	/* setup Auto Request/Age register */
 	writel(autoage, trng->base + STARFIVE_AUTO_AGE);
 	writel(autoreq, trng->base + STARFIVE_AUTO_RQSTS);
 
 	/* clear register: ISTAT */
-	starfive_trng_irq_mask_clear(trng);
+	starfive_trng_irq_clear(trng);
 
 	intr |= STARFIVE_IE_ALL;
 	writel(intr, trng->base + STARFIVE_IE);
@@ -201,45 +252,105 @@ 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);
+
+	mutex_unlock(&trng->lock);
+
+	pm_runtime_put_autosuspend(trng->dev);
+
+	return ret;
+}
+
+static void starfive_trng_randreseed_work(struct work_struct *work)
+{
+	struct starfive_trng *trng = work_to_trng(work);
+	int ret;
+
+	ret = pm_runtime_resume_and_get(trng->dev);
+	if (ret < 0) {
+		dev_warn(trng->dev, "Failed to wake device for reseed: %d\n", ret);
+		return;
+	}
+
+	mutex_lock(&trng->lock);
+
+	if (READ_ONCE(trng->cleanup))
+		goto unlock;
+
+	reinit_completion(&trng->reseed_done);
+	writel(STARFIVE_CTRL_EXEC_RANDRESEED, trng->base + STARFIVE_CTRL);
+
+unlock:
+	mutex_unlock(&trng->lock);
+
+	pm_runtime_put_autosuspend(trng->dev);
 }
 
 static irqreturn_t starfive_trng_irq(int irq, void *priv)
 {
+	int ret;
 	u32 status;
 	struct starfive_trng *trng = (struct starfive_trng *)priv;
 
+	ret = pm_runtime_get_if_active(trng->dev);
+	if (ret <= 0) {
+		dev_err_ratelimited(trng->dev, "pm is inactive in irq\n");
+		return IRQ_NONE;
+	}
+
 	status = readl(trng->base + STARFIVE_ISTAT);
-	if (status & STARFIVE_ISTAT_RAND_RDY) {
+	if (status & STARFIVE_ISTAT_RAND_RDY)
 		writel(STARFIVE_ISTAT_RAND_RDY, trng->base + STARFIVE_ISTAT);
-		complete(&trng->random_done);
-	}
 
-	if (status & STARFIVE_ISTAT_SEED_DONE) {
+	if (status & STARFIVE_ISTAT_SEED_DONE)
 		writel(STARFIVE_ISTAT_SEED_DONE, trng->base + STARFIVE_ISTAT);
-		complete(&trng->reseed_done);
-	}
 
 	if (status & STARFIVE_ISTAT_LFSR_LOCKUP) {
 		writel(STARFIVE_ISTAT_LFSR_LOCKUP, trng->base + STARFIVE_ISTAT);
 		/* SEU occurred, reseeding required*/
-		spin_lock(&trng->write_lock);
-		writel(STARFIVE_CTRL_EXEC_RANDRESEED, trng->base + STARFIVE_CTRL);
-		spin_unlock(&trng->write_lock);
+		schedule_work(&trng->work);
 	}
 
+	if (status & STARFIVE_ISTAT_RAND_RDY)
+		complete(&trng->random_done);
+
+	if (status & STARFIVE_ISTAT_SEED_DONE)
+		complete(&trng->reseed_done);
+
+	pm_runtime_put_noidle(trng->dev);
+
 	return IRQ_HANDLED;
 }
 
 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_warn(trng->dev, "Failed to wake device for cleanup: %d\n", ret);
+		goto end;
+	}
+
+	mutex_lock(&trng->lock);
+
+	writel(0, trng->base + STARFIVE_IE);
+	starfive_trng_irq_clear(trng);
+
+	if (trng->irq >= 0)
+		synchronize_irq(trng->irq);
 
 	writel(0, trng->base + STARFIVE_CTRL);
 
-	reset_control_assert(trng->rst);
-	clk_disable_unprepare(trng->hclk);
-	clk_disable_unprepare(trng->ahb);
+	WRITE_ONCE(trng->cleanup, 1);
+
+	mutex_unlock(&trng->lock);
+
+	pm_runtime_put_sync(trng->dev);
+
+end:
+	cancel_work_sync(&trng->work);
 }
 
 static int starfive_trng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
@@ -247,7 +358,18 @@ 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(trng->dev, "Failed to wake device for read: %d\n", ret);
+		return ret;
+	}
+
+	if (wait) {
+		mutex_lock(&trng->lock);
+	} else {
+		if (!mutex_trylock(&trng->lock))
+			return -EAGAIN;
+	}
 
 	if (trng->mode == PRNG_256BIT)
 		max = min_t(size_t, max, (STARFIVE_RAND_LEN * 8));
@@ -256,28 +378,29 @@ static int starfive_trng_read(struct hwrng *rng, void *buf, size_t max, bool wai
 
 	if (wait) {
 		ret = starfive_trng_wait_idle(trng);
-		if (ret) {
-			ret = -ETIMEDOUT;
-			goto out_put;
-		}
+		if (ret)
+			goto end;
 	}
 
 	ret = starfive_trng_cmd(trng, STARFIVE_CTRL_GENE_RANDNUM, wait);
 	if (ret)
-		goto out_put;
+		goto end;
 
 	memcpy_fromio(buf, trng->base + STARFIVE_RAND0, max);
+
 	ret = max;
 
-out_put:
-	pm_runtime_put_sync_autosuspend(trng->dev);
+end:
+	mutex_unlock(&trng->lock);
+
+	pm_runtime_put_autosuspend(trng->dev);
+
 	return ret;
 }
 
 static int starfive_trng_probe(struct platform_device *pdev)
 {
 	int ret;
-	int irq;
 	struct starfive_trng *trng;
 
 	trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
@@ -285,26 +408,22 @@ static int starfive_trng_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	platform_set_drvdata(pdev, trng);
+
 	trng->dev = &pdev->dev;
+	trng->data = of_device_get_match_data(&pdev->dev);
+	if (!trng->data)
+		return -EINVAL;
+
+	if (trng->data->seq_rst_clk != SEQ_RST_FIRST && trng->data->seq_rst_clk != SEQ_CLK_FIRST) {
+		dev_err(&pdev->dev, "Unknown seq_rst_clk value\n");
+		return -EINVAL;
+	}
 
 	trng->base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(trng->base))
 		return dev_err_probe(&pdev->dev, PTR_ERR(trng->base),
 				     "Error remapping memory for platform device.\n");
 
-	irq = platform_get_irq(pdev, 0);
-	if (irq < 0)
-		return irq;
-
-	init_completion(&trng->random_done);
-	init_completion(&trng->reseed_done);
-	spin_lock_init(&trng->write_lock);
-
-	ret = devm_request_irq(&pdev->dev, irq, starfive_trng_irq, 0, pdev->name,
-			       (void *)trng);
-	if (ret)
-		return ret;
-
 	trng->hclk = devm_clk_get(&pdev->dev, "hclk");
 	if (IS_ERR(trng->hclk))
 		return dev_err_probe(&pdev->dev, PTR_ERR(trng->hclk),
@@ -320,9 +439,14 @@ 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");
 
-	clk_prepare_enable(trng->hclk);
-	clk_prepare_enable(trng->ahb);
-	reset_control_deassert(trng->rst);
+	init_completion(&trng->random_done);
+	init_completion(&trng->reseed_done);
+	mutex_init(&trng->lock);
+	INIT_WORK(&trng->work, starfive_trng_randreseed_work);
+
+	trng->irq = platform_get_irq(pdev, 0);
+	if (trng->irq < 0)
+		return trng->irq;
 
 	trng->rng.name = dev_driver_string(&pdev->dev);
 	trng->rng.init = starfive_trng_init;
@@ -333,40 +457,86 @@ static int starfive_trng_probe(struct platform_device *pdev)
 	trng->mission = 1;
 	trng->reseed = RANDOM_RESEED;
 
-	pm_runtime_use_autosuspend(&pdev->dev);
-	pm_runtime_set_autosuspend_delay(&pdev->dev, 100);
-	pm_runtime_enable(&pdev->dev);
+	ret = clk_prepare_enable(trng->hclk);
+	if (ret) {
+		dev_err(&pdev->dev, "hclk clk_enable failed: %d\n", ret);
+		return ret;
+	}
 
-	ret = devm_hwrng_register(&pdev->dev, &trng->rng);
+	ret = clk_prepare_enable(trng->ahb);
 	if (ret) {
-		pm_runtime_disable(&pdev->dev);
+		clk_disable_unprepare(trng->hclk);
+		dev_err(&pdev->dev, "ahb clk_enable failed: %d\n", ret);
+		return ret;
+	}
 
-		reset_control_assert(trng->rst);
+	ret = reset_control_deassert(trng->rst);
+	if (ret) {
 		clk_disable_unprepare(trng->ahb);
 		clk_disable_unprepare(trng->hclk);
+		dev_err(&pdev->dev, "failed to deassert trng\n");
+		return ret;
+	}
 
-		return dev_err_probe(&pdev->dev, ret, "Failed to register hwrng\n");
+	pm_runtime_use_autosuspend(&pdev->dev);
+	pm_runtime_set_autosuspend_delay(&pdev->dev, 100);
+	devm_pm_runtime_set_active_enabled(&pdev->dev);
+
+	ret = devm_request_irq(&pdev->dev, trng->irq, starfive_trng_irq, 0, pdev->name,
+			       (void *)trng);
+	if (ret) {
+		starfive_trng_release(trng);
+		return dev_err_probe(&pdev->dev, ret, "Failed to register interrupt handler\n");
 	}
 
+	ret = devm_add_action_or_reset(&pdev->dev, starfive_trng_release, trng);
+	if (ret)
+		return ret;
+
+	ret = devm_hwrng_register(&pdev->dev, &trng->rng);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret, "Failed to register hwrng\n");
+
 	return 0;
 }
 
 static int __maybe_unused starfive_trng_suspend(struct device *dev)
 {
 	struct starfive_trng *trng = dev_get_drvdata(dev);
+	bool cleanup = READ_ONCE(trng->cleanup);
+
+	if (cleanup && trng->data->seq_rst_clk == SEQ_RST_FIRST)
+		reset_control_assert(trng->rst);
 
-	clk_disable_unprepare(trng->hclk);
 	clk_disable_unprepare(trng->ahb);
+	clk_disable_unprepare(trng->hclk);
+
+	if (cleanup && trng->data->seq_rst_clk == SEQ_CLK_FIRST)
+		reset_control_assert(trng->rst);
 
 	return 0;
 }
 
 static int __maybe_unused starfive_trng_resume(struct device *dev)
 {
+	int ret;
 	struct starfive_trng *trng = dev_get_drvdata(dev);
 
-	clk_prepare_enable(trng->hclk);
-	clk_prepare_enable(trng->ahb);
+	ret = clk_prepare_enable(trng->hclk);
+	if (ret) {
+		dev_err(trng->dev, "hclk clk_enable failed: %d\n", ret);
+		return ret;
+	}
+
+	ret = clk_prepare_enable(trng->ahb);
+	if (ret) {
+		clk_disable_unprepare(trng->hclk);
+		dev_err(trng->dev, "ahb clk_enable failed: %d\n", ret);
+		return ret;
+	}
+
+	if (READ_ONCE(trng->cleanup))
+		reset_control_deassert(trng->rst);
 
 	return 0;
 }
@@ -378,8 +548,17 @@ static const struct dev_pm_ops starfive_trng_pm_ops = {
 			   starfive_trng_resume, NULL)
 };
 
-static const struct of_device_id trng_dt_ids[] __maybe_unused = {
-	{ .compatible = "starfive,jh7110-trng" },
+static const struct starfive_trng_data jh7110_data = {
+	.seq_rst_clk = SEQ_RST_FIRST,
+};
+
+static const struct starfive_trng_data jhb100_data = {
+	.seq_rst_clk = SEQ_CLK_FIRST,
+};
+
+static const struct of_device_id trng_dt_ids[] = {
+	{ .compatible = "starfive,jh7110-trng", .data = &jh7110_data },
+	{ .compatible = "starfive,jhb100-trng", .data = &jhb100_data },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, trng_dt_ids);
@@ -389,7 +568,7 @@ static struct platform_driver starfive_trng_driver = {
 	.driver	= {
 		.name		= "jh7110-trng",
 		.pm		= &starfive_trng_pm_ops,
-		.of_match_table	= of_match_ptr(trng_dt_ids),
+		.of_match_table	= trng_dt_ids,
 	},
 };
 
-- 
2.43.0