2014-04-10 19:22:26

by Matt Porter

Subject: [PATCH] hwrng: bcm2835: fix oops when rng h/w is accessed during registration

Commit "d9e7972 hwrng: add randomness to system from rng sources"
exposed a bug in the bcm2835-rng driver resulting in boot failure
on Raspberry Pi due to the following oops:

[ 28.261523] BUG: soft lockup - CPU#0 stuck for 23s! [swapper:1]
[ 28.271058]
[ 28.275958] CPU: 0 PID: 1 Comm: swapper Not tainted 3.14.0+ #11
[ 28.285374] task: db480000 ti: db484000 task.ti: db484000
[ 28.294279] PC is at bcm2835_rng_read+0x28/0x48
[ 28.302276] LR is at hwrng_register+0x1a8/0x238
.
.
.

The RNG h/w is not completely initialized and enabled before
hwrng_register() is called and so the bcm2835_rng_read() fails.
Fix this by making the warmup/enable writes before registering
the RNG source with the hwrng core.

Signed-off-by: Matt Porter <[email protected]>
---
drivers/char/hw_random/bcm2835-rng.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/char/hw_random/bcm2835-rng.c b/drivers/char/hw_random/bcm2835-rng.c
index 8c3b255..e900961 100644
--- a/drivers/char/hw_random/bcm2835-rng.c
+++ b/drivers/char/hw_random/bcm2835-rng.c
@@ -61,18 +61,18 @@ static int bcm2835_rng_probe(struct platform_device *pdev)
}
bcm2835_rng_ops.priv = (unsigned long)rng_base;

+ /* set warm-up count & enable */
+ __raw_writel(RNG_WARMUP_COUNT, rng_base + RNG_STATUS);
+ __raw_writel(RNG_RBGEN, rng_base + RNG_CTRL);
+
/* register driver */
err = hwrng_register(&bcm2835_rng_ops);
if (err) {
dev_err(dev, "hwrng registration failed\n");
iounmap(rng_base);
- } else {
+ } else
dev_info(dev, "hwrng registered\n");

- /* set warm-up count & enable */
- __raw_writel(RNG_WARMUP_COUNT, rng_base + RNG_STATUS);
- __raw_writel(RNG_RBGEN, rng_base + RNG_CTRL);
- }
return err;
}

--
1.8.4

2014-04-11 03:33:10

by Herbert Xu

Subject: Re: [PATCH] hwrng: bcm2835: fix oops when rng h/w is accessed during registration

On Thu, Apr 10, 2014 at 03:22:10PM -0400, Matt Porter wrote:
> Commit "d9e7972 hwrng: add randomness to system from rng sources"
> exposed a bug in the bcm2835-rng driver resulting in boot failure
> on Raspberry Pi due to the following oops:
>
> [ 28.261523] BUG: soft lockup - CPU#0 stuck for 23s! [swapper:1]
> [ 28.271058]
> [ 28.275958] CPU: 0 PID: 1 Comm: swapper Not tainted 3.14.0+ #11
> [ 28.285374] task: db480000 ti: db484000 task.ti: db484000
> [ 28.294279] PC is at bcm2835_rng_read+0x28/0x48
> [ 28.302276] LR is at hwrng_register+0x1a8/0x238
> .
> .
> .
>
> The RNG h/w is not completely initialized and enabled before
> hwrng_register() is called and so the bcm2835_rng_read() fails.
> Fix this by making the warmup/enable writes before registering
> the RNG source with the hwrng core.
>
> Signed-off-by: Matt Porter <[email protected]>

Patch applied. Thanks a lot!
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt