[PATCH v3] hwrng: bcm2835: set quality

[Álvaro Fernández Rojas]

This allows devices without a high precission timer to speed up boot from
more than 100s to lest than 30s.

BCM2835 rngtest:
root@OpenWrt:/# cat /dev/hwrng | rngtest -c 1000
rngtest 6.10
Copyright (c) 2004 by Henrique de Moraes Holschuh
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

rngtest: starting FIPS tests...
rngtest: bits received from input: 20000032
rngtest: FIPS 140-2 successes: 996
rngtest: FIPS 140-2 failures: 4
rngtest: FIPS 140-2(2001-10-10) Monobit: 0
rngtest: FIPS 140-2(2001-10-10) Poker: 0
rngtest: FIPS 140-2(2001-10-10) Runs: 1
rngtest: FIPS 140-2(2001-10-10) Long run: 3
rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
rngtest: input channel speed: (min=146.002; avg=349.394;
max=1302083.333)Kibits/s
rngtest: FIPS tests speed: (min=12.126; avg=22.750; max=23.432)Mibits/s
rngtest: Program run time: 56826982 microseconds

996 successes and 4 failures -> 99.6% success rate
1024 * 99.6% = 1019 (rounded down to 1000)

BCM6368 rngtest:
root@OpenWrt:/# root@OpenWrt:/# cat /dev/hwrng | rngtest -c 1000
rngtest 6.10
Copyright (c) 2004 by Henrique de Moraes Holschuh
This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

rngtest: starting FIPS tests...
rngtest: bits received from input: 20000032
rngtest: FIPS 140-2 successes: 751
rngtest: FIPS 140-2 failures: 249
rngtest: FIPS 140-2(2001-10-10) Monobit: 0
rngtest: FIPS 140-2(2001-10-10) Poker: 34
rngtest: FIPS 140-2(2001-10-10) Runs: 245
rngtest: FIPS 140-2(2001-10-10) Long run: 0
rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
rngtest: input channel speed: (min=1.202; avg=16.434; max=1003.868)Mibits/s
rngtest: FIPS tests speed: (min=761.155; avg=8343.383; max=15662.590)Kibits/s
rngtest: Program run time: 3539183 microseconds
cat: write error: Broken pipe

Signed-off-by: Álvaro Fernández Rojas <noltari@xxxxxxxxx>
---
 v3: set different qualities for each SoC
 v2: add jusftification

 drivers/char/hw_random/bcm2835-rng.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/char/hw_random/bcm2835-rng.c b/drivers/char/hw_random/bcm2835-rng.c
index 1a7c43b43c6b..a6121a04f624 100644
--- a/drivers/char/hw_random/bcm2835-rng.c
+++ b/drivers/char/hw_random/bcm2835-rng.c
@@ -121,6 +121,15 @@ static void bcm2835_rng_cleanup(struct hwrng *rng)
 
 struct bcm2835_rng_of_data {
 	bool mask_interrupts;
+	unsigned short quality;
+};
+
+static const struct bcm2835_rng_of_data bcm283x_rng_of_data = {
+	.quality = 1000,
+};
+
+static const struct bcm2835_rng_of_data bcm6368_rng_of_data = {
+	.quality = 700,
 };
 
 static const struct bcm2835_rng_of_data nsp_rng_of_data = {
@@ -128,10 +137,10 @@ static const struct bcm2835_rng_of_data nsp_rng_of_data = {
 };
 
 static const struct of_device_id bcm2835_rng_of_match[] = {
-	{ .compatible = "brcm,bcm2835-rng"},
+	{ .compatible = "brcm,bcm2835-rng", .data = &bcm283x_rng_of_data },
 	{ .compatible = "brcm,bcm-nsp-rng", .data = &nsp_rng_of_data },
 	{ .compatible = "brcm,bcm5301x-rng", .data = &nsp_rng_of_data },
-	{ .compatible = "brcm,bcm6368-rng"},
+	{ .compatible = "brcm,bcm6368-rng", .data = &bcm6368_rng_of_data },
 	{},
 };
 
@@ -171,8 +180,10 @@ static int bcm2835_rng_probe(struct platform_device *pdev)
 
 		/* Check for rng init function, execute it */
 		of_data = rng_id->data;
-		if (of_data)
+		if (of_data) {
 			priv->mask_interrupts = of_data->mask_interrupts;
+			priv->rng.quality = of_data->quality;
+		}
 	}
 
 	/* register driver */
-- 
2.20.1