diff options
Diffstat (limited to 'drivers/char/hw_random/bcm2835-rng.c')
| -rw-r--r-- | drivers/char/hw_random/bcm2835-rng.c | 26 |
1 files changed, 18 insertions, 8 deletions
diff --git a/drivers/char/hw_random/bcm2835-rng.c b/drivers/char/hw_random/bcm2835-rng.c index aa2b135e3ee2..05a4569ce28f 100644 --- a/drivers/char/hw_random/bcm2835-rng.c +++ b/drivers/char/hw_random/bcm2835-rng.c @@ -13,6 +13,7 @@ #include <linux/printk.h> #include <linux/clk.h> #include <linux/reset.h> +#include <linux/delay.h> #define RNG_CTRL 0x0 #define RNG_STATUS 0x4 @@ -27,6 +28,9 @@ #define RNG_INT_OFF 0x1 +#define RNG_FIFO_WORDS 4 +#define RNG_US_PER_WORD 34 /* Tuned for throughput */ + struct bcm2835_rng_priv { struct hwrng rng; void __iomem *base; @@ -63,19 +67,23 @@ static inline void rng_writel(struct bcm2835_rng_priv *priv, u32 val, static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait) { + u32 retries = 1000000/(RNG_FIFO_WORDS * RNG_US_PER_WORD); struct bcm2835_rng_priv *priv = to_rng_priv(rng); u32 max_words = max / sizeof(u32); u32 num_words, count; - while ((rng_readl(priv, RNG_STATUS) >> 24) == 0) { - if (!wait) + num_words = rng_readl(priv, RNG_STATUS) >> 24; + + while (!num_words) { + if (!wait || !retries) return 0; - hwrng_yield(rng); + retries--; + usleep_range((u32)RNG_US_PER_WORD, + (u32)RNG_US_PER_WORD * RNG_FIFO_WORDS); + num_words = rng_readl(priv, RNG_STATUS) >> 24; } - num_words = rng_readl(priv, RNG_STATUS) >> 24; - if (num_words > max_words) - num_words = max_words; + num_words = min(num_words, max_words); for (count = 0; count < num_words; count++) ((u32 *)buf)[count] = rng_readl(priv, RNG_DATA); @@ -107,8 +115,10 @@ static int bcm2835_rng_init(struct hwrng *rng) } /* set warm-up count & enable */ - rng_writel(priv, RNG_WARMUP_COUNT, RNG_STATUS); - rng_writel(priv, RNG_RBGEN, RNG_CTRL); + if (!(rng_readl(priv, RNG_CTRL) & RNG_RBGEN)) { + rng_writel(priv, RNG_WARMUP_COUNT, RNG_STATUS); + rng_writel(priv, RNG_RBGEN, RNG_CTRL); + } return ret; } |