RE: [PATCH 3/5] rng: Add StarFive JH7110 RNG driver

["Chanho Park" <chanho61.park@samsung.com>]

> -----Original Message-----
> From: Heinrich Schuchardt <xypron.glpk@gmx.de>
> Sent: Wednesday, November 1, 2023 6:18 AM
> To: Chanho Park <chanho61.park@samsung.com>
> Cc: Sughosh Ganu <sughosh.ganu@linaro.org>; Rick Chen <rick@andestech.com>;
> Leo <ycliang@andestech.com>; u-boot@lists.denx.de
> Subject: Re: [PATCH 3/5] rng: Add StarFive JH7110 RNG driver
> 
> On 10/30/23 09:32, Chanho Park wrote:
> > Adds to support JH7110 TRNG driver which is based on linux kernel's
> > jh7110-trng.c. This can support to generate 256-bit random numbers and
> > 128-bit but this makes 256-bit default for convenience.
> >
> > Signed-off-by: Chanho Park <chanho61.park@samsung.com>
> > ---
> >   drivers/rng/Kconfig      |   6 +
> >   drivers/rng/Makefile     |   1 +
> >   drivers/rng/jh7110_rng.c | 272 +++++++++++++++++++++++++++++++++++++++
> >   3 files changed, 279 insertions(+)
> >   create mode 100644 drivers/rng/jh7110_rng.c
> >
> > diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig
> > index 994cc35b2744..0dba1e06b429 100644
> > --- a/drivers/rng/Kconfig
> > +++ b/drivers/rng/Kconfig
> > @@ -91,4 +91,10 @@ config TPM_RNG
> >   	  functionality. Enable random number generator on TPM
> >   	  devices.
> >
> > +config RNG_JH7110
> > +	bool "StarFive JH7110 Random Number Generator support"
> > +	depends on DM_RNG && STARFIVE_JH7110
> > +	help
> > +	  Enable True Random Number Generator in StarFive JH7110 SoCs.
> > +
> >   endif
> > diff --git a/drivers/rng/Makefile b/drivers/rng/Makefile
> > index 47b323e61ee3..9de762c8a1c3 100644
> > --- a/drivers/rng/Makefile
> > +++ b/drivers/rng/Makefile
> > @@ -15,3 +15,4 @@ obj-$(CONFIG_RNG_IPROC200) += iproc_rng200.o
> >   obj-$(CONFIG_RNG_SMCCC_TRNG) += smccc_trng.o
> >   obj-$(CONFIG_RNG_ARM_RNDR) += arm_rndr.o
> >   obj-$(CONFIG_TPM_RNG) += tpm_rng.o
> > +obj-$(CONFIG_RNG_JH7110) += jh7110_rng.o
> > diff --git a/drivers/rng/jh7110_rng.c b/drivers/rng/jh7110_rng.c
> > new file mode 100644
> > index 000000000000..e71bf188f017
> > --- /dev/null
> > +++ b/drivers/rng/jh7110_rng.c
> > @@ -0,0 +1,272 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * TRNG driver for the StarFive JH7110 SoC
> > + *
> > + */
> > +
> > +#include <clk.h>
> > +#include <dm.h>
> > +#include <reset.h>
> > +#include <rng.h>
> > +#include <asm/io.h>
> > +#include <linux/iopoll.h>
> > +
> > +/* trng register offset */
> > +#define STARFIVE_CTRL			0x00
> > +#define STARFIVE_STAT			0x04
> > +#define STARFIVE_MODE			0x08
> > +#define STARFIVE_SMODE			0x0C
> > +#define STARFIVE_IE			0x10
> > +#define STARFIVE_ISTAT			0x14
> > +#define STARFIVE_RAND0			0x20
> > +#define STARFIVE_RAND1			0x24
> > +#define STARFIVE_RAND2			0x28
> > +#define STARFIVE_RAND3			0x2C
> > +#define STARFIVE_RAND4			0x30
> > +#define STARFIVE_RAND5			0x34
> > +#define STARFIVE_RAND6			0x38
> > +#define STARFIVE_RAND7			0x3C
> > +#define STARFIVE_AUTO_RQSTS		0x60
> > +#define STARFIVE_AUTO_AGE		0x64
> > +
> > +/* CTRL CMD */
> > +#define STARFIVE_CTRL_EXEC_NOP		0x0
> > +#define STARFIVE_CTRL_GENE_RANDNUM	0x1
> > +#define STARFIVE_CTRL_EXEC_RANDRESEED	0x2
> > +
> > +/* STAT */
> > +#define STARFIVE_STAT_NONCE_MODE	BIT(2)
> > +#define STARFIVE_STAT_R256		BIT(3)
> > +#define STARFIVE_STAT_MISSION_MODE	BIT(8)
> > +#define STARFIVE_STAT_SEEDED		BIT(9)
> > +#define STARFIVE_STAT_LAST_RESEED(x)	((x) << 16)
> > +#define STARFIVE_STAT_SRVC_RQST		BIT(27)
> > +#define STARFIVE_STAT_RAND_GENERATING	BIT(30)
> > +#define STARFIVE_STAT_RAND_SEEDING	BIT(31)
> > +#define STARFIVE_STAT_RUNNING		(STARFIVE_STAT_RAND_GENERATING | \
> > +					 STARFIVE_STAT_RAND_SEEDING)
> > +
> > +/* MODE */
> > +#define STARFIVE_MODE_R256		BIT(3)
> > +
> > +/* SMODE */
> > +#define STARFIVE_SMODE_NONCE_MODE	BIT(2)
> > +#define STARFIVE_SMODE_MISSION_MODE	BIT(8)
> > +#define STARFIVE_SMODE_MAX_REJECTS(x)	((x) << 16)
> > +
> > +/* IE */
> > +#define STARFIVE_IE_RAND_RDY_EN		BIT(0)
> > +#define STARFIVE_IE_SEED_DONE_EN	BIT(1)
> > +#define STARFIVE_IE_LFSR_LOCKUP_EN	BIT(4)
> > +#define STARFIVE_IE_GLBL_EN		BIT(31)
> > +
> > +#define STARFIVE_IE_ALL			(STARFIVE_IE_GLBL_EN | \
> > +					 STARFIVE_IE_RAND_RDY_EN | \
> > +					 STARFIVE_IE_SEED_DONE_EN | \
> > +					 STARFIVE_IE_LFSR_LOCKUP_EN)
> > +
> > +/* ISTAT */
> > +#define STARFIVE_ISTAT_RAND_RDY		BIT(0)
> > +#define STARFIVE_ISTAT_SEED_DONE	BIT(1)
> > +#define STARFIVE_ISTAT_LFSR_LOCKUP	BIT(4)
> > +
> > +#define STARFIVE_RAND_LEN		sizeof(u32)
> > +
> > +enum mode {
> > +	PRNG_128BIT,
> > +	PRNG_256BIT,
> > +};
> > +
> > +struct starfive_trng_plat {
> > +	void *base;
> > +	struct clk *hclk;
> > +	struct clk *ahb;
> > +	struct reset_ctl *rst;
> > +	u32 mode;
> > +};
> > +
> > +static inline int starfive_trng_wait_idle(struct starfive_trng_plat
> *trng)
> > +{
> > +	u32 stat;
> > +
> > +	return readl_relaxed_poll_timeout(trng->base + STARFIVE_STAT, stat,
> > +					  !(stat & STARFIVE_STAT_RUNNING),
> > +					  100000);
> > +}
> > +
> > +static inline void starfive_trng_irq_mask_clear(struct
> starfive_trng_plat *trng)
> > +{
> > +	/* clear register: ISTAT */
> > +	u32 data = readl(trng->base + STARFIVE_ISTAT);
> > +
> > +	writel(data, trng->base + STARFIVE_ISTAT);
> > +}
> > +
> > +static int starfive_trng_cmd(struct starfive_trng_plat *trng, u32 cmd)
> > +{
> > +	u32 stat, flg;
> > +	int ret;
> > +
> > +	switch (cmd) {
> > +	case STARFIVE_CTRL_GENE_RANDNUM:
> > +		writel(cmd, trng->base + STARFIVE_CTRL);
> > +		flg = STARFIVE_ISTAT_RAND_RDY;
> > +		break;
> > +	case STARFIVE_CTRL_EXEC_RANDRESEED:
> > +		writel(cmd, trng->base + STARFIVE_CTRL);
> > +		flg = STARFIVE_ISTAT_SEED_DONE;
> > +		break;
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +
> > +	ret = readl_relaxed_poll_timeout(trng->base + STARFIVE_ISTAT, stat,
> > +					 (stat & flg), 1000);
> > +	writel(flg, trng->base + STARFIVE_ISTAT);
> > +
> > +	return ret;
> > +}
> > +
> > +static int starfive_trng_read(struct udevice *dev, void *data, size_t
> len)
> > +{
> > +	struct starfive_trng_plat *trng = dev_get_plat(dev);
> > +	char *buffer = (char *)data;
> 
> Great to see a RNG driver for this SoC.
> 
> The conversion is not needed in C and should be removed.

Thank you for your kind review.
I'll remove it in the next patch.

> 
> > +	int ret;
> > +	size_t max;
> > +
> > +	if (trng->mode == PRNG_256BIT)
> > +		max = min_t(size_t, max, (STARFIVE_RAND_LEN * 8));
> > +	else
> > +		max = min_t(size_t, max, (STARFIVE_RAND_LEN * 4));
> > +
> > +	ret = starfive_trng_wait_idle(trng);
> > +	if (ret)
> > +		return -ETIMEDOUT;
> > +
> > +	while (len) {
> > +		size_t max;
> > +		u32 val, step;
> 
> Variables should be defined in the loop where they are used.
> Use size_t for step as this is what memcpy() needs as argument.
> 
> > +
> > +		if (trng->mode == PRNG_256BIT)
> 
> The arguments of this if-statement are not changed in the loop. We don't
> really need the variable max. The number of iterations would be enough:
> 
>      if (trng->mode == PRNG_256BIT)
>          rounds = 8;
>      else
>          rounds = 4;
>      while(len) {
> 
> > +			max = min_t(size_t, len, (STARFIVE_RAND_LEN * 8));
> > +		else
> > +			max = min_t(size_t, len, (STARFIVE_RAND_LEN * 4));
> > +
> > +		ret = starfive_trng_cmd(trng, STARFIVE_CTRL_GENE_RANDNUM);
> > +		if (ret)
> > +			return ret;
> > +
> > +		for (int i = 0; i < DIV_ROUND_UP(max, STARFIVE_RAND_LEN);
> i++) {
> 
> You are decrementing max in the loop. So on every iteration
> DIV_ROUND_UP(max, STARFIVE_RAND_LEN) will result in different result. I
> don't believe this is intended.
> 
> > +			val = readl(trng->base + STARFIVE_RAND0 +
> > +				    (i * STARFIVE_RAND_LEN));
> > +			step = (max >= STARFIVE_RAND_LEN) ?
> > +				STARFIVE_RAND_LEN : max;
> 
> Please, stay consistent in your style and use min_t().
> 
> > +			memcpy(buffer, &val, step);
> > +
> > +			max -= step;
> > +			buffer += step;
> > +			len -= step;
> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> 
> The following code looks a bit easier to read:
> 
> u8 *buffer = data;
> int iter_mask;
> 
> if (trng->mode == PRNG_256BIT)
>      iter_mask = 7;
> else
>      iter_mask = 3;
> 
> for (int i = 0; len; ++i, i &= iter_mask)
>      u32 val;
>      size_t step;
> 
>      if (!i) {
>           int ret;
> 
>           ret = starfive_trng_wait_idle(trng);
>           if (ret)
>                return -ETIMEDOUT;
>       }
>       val = read_l(trng->base + STARFIVE_RAND0 +
>             (i * STARFIVE_RAND_LEN));
>       step = min_t(size_t, len, STARFIVE_RAND_LEN);
>       memcpy (buffer, &val, step);
>       len -= step;
> }

That's a good suggestion, so let's apply the code.

Best Regards,
Chanho Park

> 
> Best regards
> 
> Heinrich
> 
> > +
> > +static int starfive_trng_init(struct starfive_trng_plat *trng)
> > +{
> > +	u32 mode, intr = 0;
> > +
> > +	/* setup Auto Request/Age register */
> > +	writel(0, trng->base + STARFIVE_AUTO_AGE);
> > +	writel(0, trng->base + STARFIVE_AUTO_RQSTS);
> > +
> > +	/* clear register: ISTAT */
> > +	starfive_trng_irq_mask_clear(trng);
> > +
> > +	intr |= STARFIVE_IE_ALL;
> > +	writel(intr, trng->base + STARFIVE_IE);
> > +
> > +	mode = readl(trng->base + STARFIVE_MODE);
> > +
> > +	switch (trng->mode) {
> > +	case PRNG_128BIT:
> > +		mode &= ~STARFIVE_MODE_R256;
> > +		break;
> > +	case PRNG_256BIT:
> > +		mode |= STARFIVE_MODE_R256;
> > +		break;
> > +	default:
> > +		mode |= STARFIVE_MODE_R256;
> > +		break;
> > +	}
> > +
> > +	writel(mode, trng->base + STARFIVE_MODE);
> > +
> > +	return starfive_trng_cmd(trng, STARFIVE_CTRL_EXEC_RANDRESEED);
> > +}
> > +
> > +static int starfive_trng_probe(struct udevice *dev)
> > +{
> > +	struct starfive_trng_plat *pdata = dev_get_plat(dev);
> > +	int err;
> > +
> > +	err = clk_enable(pdata->hclk);
> > +	if (err)
> > +		return err;
> > +
> > +	err = clk_enable(pdata->ahb);
> > +	if (err)
> > +		return err;
> > +
> > +	err = reset_deassert(pdata->rst);
> > +	if (err)
> > +		return err;
> > +
> > +	pdata->mode = PRNG_256BIT;
> > +
> > +	return starfive_trng_init(pdata);
> > +}
> > +
> > +static int starfive_trng_of_to_plat(struct udevice *dev)
> > +{
> > +	struct starfive_trng_plat *pdata = dev_get_plat(dev);
> > +
> > +	pdata->base = (void *)dev_read_addr(dev);
> > +	if (!pdata->base)
> > +		return -ENODEV;
> > +
> > +	pdata->hclk = devm_clk_get(dev, "hclk");
> > +	if (IS_ERR(pdata->hclk))
> > +		return -ENODEV;
> > +
> > +	pdata->ahb = devm_clk_get(dev, "ahb");
> > +	if (IS_ERR(pdata->ahb))
> > +		return -ENODEV;
> > +
> > +	pdata->rst = devm_reset_control_get(dev, NULL);
> > +	if (IS_ERR(pdata->rst))
> > +		return -ENODEV;
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct dm_rng_ops starfive_trng_ops = {
> > +	.read = starfive_trng_read,
> > +};
> > +
> > +static const struct udevice_id starfive_trng_match[] = {
> > +	{
> > +		.compatible = "starfive,jh7110-trng",
> > +	},
> > +	{},
> > +};
> > +
> > +U_BOOT_DRIVER(starfive_trng) = {
> > +	.name = "jh7110-trng",
> > +	.id = UCLASS_RNG,
> > +	.of_match = starfive_trng_match,
> > +	.probe = starfive_trng_probe,
> > +	.ops = &starfive_trng_ops,
> > +	.plat_auto = sizeof(struct starfive_trng_plat),
> > +	.of_to_plat = starfive_trng_of_to_plat,
> > +};