From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
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: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
---
drivers/char/hw_random/ks-sa-rng.c | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)
diff --git a/drivers/char/hw_random/ks-sa-rng.c b/drivers/char/hw_random/ks-sa-rng.c
index a674300..4b223cb 100644
--- a/drivers/char/hw_random/ks-sa-rng.c
+++ b/drivers/char/hw_random/ks-sa-rng.c
@@ -21,6 +21,7 @@
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/delay.h>
+#include <linux/timekeeping.h>
#define SA_CMD_STATUS_OFS 0x8
@@ -85,13 +86,36 @@ struct ks_sa_rng {
struct clk *clk;
struct regmap *regmap_cfg;
struct trng_regs *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)
{
u32 value;
struct device *dev = (struct device *)rng->priv;
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 */
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;
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;
}
@@ -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);
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;
}
@@ -152,10 +181,19 @@ static int ks_sa_rng_data_present(struct hwrng *rng, int wait)
{
struct device *dev = (struct device *)rng->priv;
struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
+ u64 now = ktime_get_ns();
u32 ready;
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++) {
ready = readl(&ks_sa_rng->reg_rng->status);
ready &= TRNG_STATUS_REG_READY;
--
2.4.6
