Commit 6d01d851 authored by Alexander Sverdlin's avatar Alexander Sverdlin Committed by Herbert Xu
Browse files

hwrng: ks-sa - Add minimum sleep time before ready-polling 



Current polling timeout is 25 us. The hardware is currently configured to
harvest the entropy for 81920 us. This leads to timeouts even during
blocking read (wait=1).

Log snippet:
[    5.727589] [<c040ffcc>] (ks_sa_rng_probe) from [<c04181e8>] (platform_drv_probe+0x58/0xb4)
...
[    5.727805] hwrng: no data available
...
[   13.157016] random: systemd: uninitialized urandom read (16 bytes read)
[   13.157033] systemd[1]: Initializing machine ID from random generator.
...
[   15.848770] random: fast init done
...
[   15.848807] random: crng init done

After the patch:
[    6.223534] random: systemd: uninitialized urandom read (16 bytes read)
[    6.223551] systemd[1]: Initializing machine ID from random generator.
...
[    6.876075] random: fast init done
...
[    6.954200] random: systemd: uninitialized urandom read (16 bytes read)
[    6.955244] random: systemd: uninitialized urandom read (16 bytes read)
...
[    7.121948] random: crng init done

Signed-off-by: default avatarAlexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 698b2227

drivers/char/hw_random/ks-sa-rng.c

+38 −0
Original line number Original line Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <linux/of.h>

#include <linux/of.h>

#include <linux/of_address.h>

#include <linux/of_address.h>

#include <linux/delay.h>

#include <linux/delay.h>

#include <linux/timekeeping.h>





#define SA_CMD_STATUS_OFS			0x8

#define SA_CMD_STATUS_OFS			0x8
@@ -85,13 +86,36 @@ struct ks_sa_rng { 
	struct clk	*clk;

	struct clk	*clk;

	struct regmap	*regmap_cfg;

	struct regmap	*regmap_cfg;

	struct trng_regs __iomem *reg_rng;

	struct trng_regs __iomem *reg_rng;

	u64 ready_ts;

	unsigned int refill_delay_ns;

};

};





static unsigned int cycles_to_ns(unsigned long clk_rate, unsigned int cycles)

{

	return DIV_ROUND_UP_ULL((TRNG_DEF_CLK_DIV_CYCLES + 1) * 1000000000ull *

				cycles, clk_rate);

}



static unsigned int startup_delay_ns(unsigned long clk_rate)

{

	if (!TRNG_DEF_STARTUP_CYCLES)

		return cycles_to_ns(clk_rate, BIT(24));

	return cycles_to_ns(clk_rate, 256 * TRNG_DEF_STARTUP_CYCLES);

}



static unsigned int refill_delay_ns(unsigned long clk_rate)

{

	if (!TRNG_DEF_MAX_REFILL_CYCLES)

		return cycles_to_ns(clk_rate, BIT(24));

	return cycles_to_ns(clk_rate, 256 * TRNG_DEF_MAX_REFILL_CYCLES);

}



static int ks_sa_rng_init(struct hwrng *rng)

static int ks_sa_rng_init(struct hwrng *rng)

{

{

	u32 value;

	u32 value;

	struct device *dev = (struct device *)rng->priv;

	struct device *dev = (struct device *)rng->priv;

	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);

	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);

	unsigned long clk_rate = clk_get_rate(ks_sa_rng->clk);





	/* Enable RNG module */

	/* Enable RNG module */

	regmap_write_bits(ks_sa_rng->regmap_cfg, SA_CMD_STATUS_OFS,

	regmap_write_bits(ks_sa_rng->regmap_cfg, SA_CMD_STATUS_OFS,
@@ -120,6 +144,10 @@ static int ks_sa_rng_init(struct hwrng *rng) 
	value |= TRNG_CNTL_REG_TRNG_ENABLE;

	value |= TRNG_CNTL_REG_TRNG_ENABLE;

	writel(value, &ks_sa_rng->reg_rng->control);

	writel(value, &ks_sa_rng->reg_rng->control);





	ks_sa_rng->refill_delay_ns = refill_delay_ns(clk_rate);

	ks_sa_rng->ready_ts = ktime_get_ns() +

			      startup_delay_ns(clk_rate);



	return 0;

	return 0;

}

}
@@ -144,6 +172,7 @@ static int ks_sa_rng_data_read(struct hwrng *rng, u32 *data) 
	data[1] = readl(&ks_sa_rng->reg_rng->output_h);

	data[1] = readl(&ks_sa_rng->reg_rng->output_h);





	writel(TRNG_INTACK_REG_READY, &ks_sa_rng->reg_rng->intack);

	writel(TRNG_INTACK_REG_READY, &ks_sa_rng->reg_rng->intack);

	ks_sa_rng->ready_ts = ktime_get_ns() + ks_sa_rng->refill_delay_ns;





	return sizeof(u32) * 2;

	return sizeof(u32) * 2;

}

}
@@ -152,10 +181,19 @@ static int ks_sa_rng_data_present(struct hwrng *rng, int wait) 
{

{

	struct device *dev = (struct device *)rng->priv;

	struct device *dev = (struct device *)rng->priv;

	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);

	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);

	u64 now = ktime_get_ns();





	u32	ready;

	u32	ready;

	int	j;

	int	j;





	if (wait && now < ks_sa_rng->ready_ts) {

		/* Max delay expected here is 81920000 ns */

		unsigned long min_delay =

			DIV_ROUND_UP((u32)(ks_sa_rng->ready_ts - now), 1000);



		usleep_range(min_delay, min_delay + SA_RNG_DATA_RETRY_DELAY);

	}



	for (j = 0; j < SA_MAX_RNG_DATA_RETRIES; j++) {

	for (j = 0; j < SA_MAX_RNG_DATA_RETRIES; j++) {

		ready = readl(&ks_sa_rng->reg_rng->status);

		ready = readl(&ks_sa_rng->reg_rng->status);

		ready &= TRNG_STATUS_REG_READY;

		ready &= TRNG_STATUS_REG_READY;

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