linux-kernel - Re: [PATCH v2 2/3] hwrng: starfive - Add TRNG driver for StarFive SoC

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Date:   Fri, 6 Jan 2023 16:39:24 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Jia Jie Ho <jiajie.ho@...rfivetech.com>
Cc:     Olivia Mackall <olivia@...enic.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Emil Renner Berthing <kernel@...il.dk>,
        Conor Dooley <conor.dooley@...rochip.com>,
        linux-crypto@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 2/3] hwrng: starfive - Add TRNG driver for StarFive SoC

On Wed, Dec 28, 2022 at 03:11:02PM +0800, Jia Jie Ho wrote:
>
> +static int starfive_trng_cmd(struct starfive_trng *trng, u32 cmd)
> +{
> +	int ret;
> +
> +	ret = starfive_trng_wait_idle(trng);
> +	if (ret)
> +		return -ETIMEDOUT;
> +
> +	switch (cmd) {
> +	case STARFIVE_CTRL_EXEC_NOP:
> +		writel(cmd, trng->base + STARFIVE_CTRL);
> +		break;
> +	case STARFIVE_CTRL_GENE_RANDNUM:
> +		reinit_completion(&trng->random_done);
> +		writel(cmd, trng->base + STARFIVE_CTRL);
> +		ret = wait_for_completion_timeout(&trng->random_done, 3000);

Please don't use a constant jiffies value, because it may vary
in length.  Instead use a constant millisecond value and convert
it to jiffies.

> +static irqreturn_t starfive_trng_irq(int irq, void *priv)
> +{
> +	u32 status;
> +	struct starfive_trng *trng = (struct starfive_trng *)priv;
> +
> +	status = readl(trng->base + STARFIVE_ISTAT);
> +	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) {
> +		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);
> +		starfive_trng_cmd(trng, STARFIVE_CTRL_EXEC_RANDRESEED);

You should not sleep in an IRQ handler.

> +static int starfive_trng_read(struct hwrng *rng, void *buf, size_t max, bool wait)

You should respect the wait argument and not do polling/sleeping
if it is false.

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