Re: [PATCH v5 2/2] hwrng: starfive: rework clk/reset teardown order for JHB100

[Herbert Xu <herbert@gondor.apana.org.au>]

On Mon, Jun 29, 2026 at 04:36:58PM +0800, lianfeng.ouyang wrote:
> 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 | 312 +++++++++++++++++++++------
>  2 files changed, 245 insertions(+), 69 deletions(-)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d3a6b3f6b6a0..729b20ecc697 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -25280,7 +25280,7 @@ 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 9776f4daa044..1434dcb6efed 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;
> -	struct clk		*hclk;
> -	struct clk		*ahb;
> -	struct reset_control	*rst;
> -	struct hwrng		rng;
> -	struct completion	random_done;
> -	struct completion	reseed_done;
> -	u32			mode;
> -	u32			mission;
> -	u32			reseed;
> -	/* protects against concurrent write to ctrl register */
> -	spinlock_t		write_lock;
> +	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				mission;
> +	u32				reseed;
> +	u32				cleanup;
> +	struct mutex			lock; /* protect trng cmd seq */

Doing a white-space change at the same time as a substantial change
makes things hard to review.  Please split this up or just drop the
white-space change until later.
  
>  static int starfive_trng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
> @@ -247,7 +358,13 @@ 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;
> +	}
> +
> +	mutex_lock(&trng->lock);

What happens when a non-waiting read call ends up spinning here
waiting for a wait read call?

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt