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[PATCH 4/4] hwrng: bcm2835: Read as much data as available

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  [PATCH 4/4] hwrng: bcm2835: Read as much data as available Yendapally Reddy Dhananjaya Reddy <yendapally.reddy@broadcom.com> - 2016-05-23 18:30 +0200
    Re: [PATCH 4/4] hwrng: bcm2835: Read as much data as available Eric Anholt <eric@anholt.net> - 2016-05-24 04:30 +0200

#1405500 — [PATCH 4/4] hwrng: bcm2835: Read as much data as available

Read the requested number of data from the fifo

Signed-off-by: Yendapally Reddy Dhananjaya Reddy <yendapally.reddy@broadcom.com>
---
 drivers/char/hw_random/bcm2835-rng.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/char/hw_random/bcm2835-rng.c b/drivers/char/hw_random/bcm2835-rng.c
index b1e8b78..9bbdc07 100644
--- a/drivers/char/hw_random/bcm2835-rng.c
+++ b/drivers/char/hw_random/bcm2835-rng.c
@@ -43,6 +43,8 @@ static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
 			       bool wait)
 {
 	void __iomem *rng_base = (void __iomem *)rng->priv;
+	u32 max_words = max/sizeof(u32);
+	u32 num_words, count;
 
 	while ((__raw_readl(rng_base + RNG_STATUS) >> 24) == 0) {
 		if (!wait)
@@ -50,8 +52,14 @@ static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
 		cpu_relax();
 	}
 
-	*(u32 *)buf = __raw_readl(rng_base + RNG_DATA);
-	return sizeof(u32);
+	num_words = (readl(rng_base + RNG_STATUS) >> 24);
+	if (num_words > max_words)
+		num_words = max_words;
+
+	for (count = 0; count < num_words; count++)
+		((u32 *)buf)[count] = readl(rng_base + RNG_DATA);
+
+	return (num_words * sizeof(u32));
 }
 
 static struct hwrng bcm2835_rng_ops = {
-- 
2.1.0

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#1405788

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Yendapally Reddy Dhananjaya Reddy <yendapally.reddy@broadcom.com>
writes:

> Read the requested number of data from the fifo
>
> Signed-off-by: Yendapally Reddy Dhananjaya Reddy <yendapally.reddy@broadcom.com>
> ---
>  drivers/char/hw_random/bcm2835-rng.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/char/hw_random/bcm2835-rng.c b/drivers/char/hw_random/bcm2835-rng.c
> index b1e8b78..9bbdc07 100644
> --- a/drivers/char/hw_random/bcm2835-rng.c
> +++ b/drivers/char/hw_random/bcm2835-rng.c
> @@ -43,6 +43,8 @@ static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
>  			       bool wait)
>  {
>  	void __iomem *rng_base = (void __iomem *)rng->priv;
> +	u32 max_words = max/sizeof(u32);

Style fix: Binary operators get a space on each side, so
"max / sizeof(u32);"

> @@ -50,8 +52,14 @@ static int bcm2835_rng_read(struct hwrng *rng, void *buf, size_t max,
>  		cpu_relax();
>  	}
>  
> -	*(u32 *)buf = __raw_readl(rng_base + RNG_DATA);
> -	return sizeof(u32);
> +	num_words = (readl(rng_base + RNG_STATUS) >> 24);

Optional cleanup: here and in the return statement, drop the extra
parenthesis.

Functionality-wise, this patch looks great to me, and should make the
driver more efficient.  With at least the binary operators change done,
it will be:

Reviewed-by: Eric Anholt <eric@anholt.net>

Thanks!

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