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

[JiaJie Ho]

> -----Original Message-----
> From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Sent: 6 January, 2023 4:39 PM
> To: JiaJie Ho <jiajie.ho@xxxxxxxxxxxxxxxx>
> Cc: Olivia Mackall <olivia@xxxxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>;
> Krzysztof Kozlowski <krzysztof.kozlowski+dt@xxxxxxxxxx>; Emil Renner
> Berthing <kernel@xxxxxxxx>; Conor Dooley <conor.dooley@xxxxxxxxxxxxx>;
> linux-crypto@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; linux-riscv@xxxxxxxxxxxxxxxxxxx
> 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.
> 

I'll fix this in next version.

> > +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.
> 

Will fix this too.

> > +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.

I'll add this in the next version.

Thanks for reviewing this patch.

Best regards,
Jia Jie