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authorAlexander Sverdlin <alexander.sverdlin@nokia.com>2019-11-06 09:30:49 +0000
committerHerbert Xu <herbert@gondor.apana.org.au>2019-11-17 08:37:29 +0800
commit6d01d8511dceb9cd40f72eb102b7d24f0b2e997b (patch)
treee73f92591dbda36418e4b5f218fbafbc983f310e /drivers/char/hw_random
parent698b22273efa893d664e64116aa844cfb5057a5f (diff)
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: Alexander Sverdlin <alexander.sverdlin@nokia.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'drivers/char/hw_random')
-rw-r--r--drivers/char/hw_random/ks-sa-rng.c38
1 files changed, 38 insertions, 0 deletions
diff --git a/drivers/char/hw_random/ks-sa-rng.c b/drivers/char/hw_random/ks-sa-rng.c
index 3dbd6b7a65f0..e2330e757f1f 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 __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)
{
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;