[PATCH 4.10 14/27] hwrng: omap - write registers after enabling the clock

Greg Kroah-Hartman
2017-03-24T18:01:14Z

From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

commit 45c2fdde01299b02a6e3225e848598a3c1e55539 upstream.

Commit 383212425c926 ("hwrng: omap - Add device variant for SafeXcel
IP-76 found in Armada 8K") added support for the SafeXcel IP-76 variant
of the IP. This modification included getting a reference and enabling a
clock. Unfortunately, this was done *after* writing to the
RNG_INTMASK_REG register. This generally works fine when the driver is
built-in because the clock might have been left enabled by the
bootloader, but fails short when the driver is built as a module: it
causes a system hang because a register is being accessed while the
clock is not enabled.

This commit fixes that by making the register access *after* enabling
the clock.

This issue was found by the kernelci.org testing effort.

Fixes: 383212425c926 ("hwrng: omap - Add device variant for SafeXcel IP-76 found in Armada 8K")
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/char/hw_random/omap-rng.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/char/hw_random/omap-rng.c
+++ b/drivers/char/hw_random/omap-rng.c
@@ -397,7 +397,6 @@ static int of_get_omap_rng_device_detail
irq, err);
return err;
}
- omap_rng_write(priv, RNG_INTMASK_REG, RNG_SHUTDOWN_OFLO_MASK);

priv->clk = of_clk_get(pdev->dev.of_node, 0);
if (IS_ERR(priv->clk) && PTR_ERR(priv->clk) == -EPROBE_DEFER)
@@ -408,6 +407,8 @@ static int of_get_omap_rng_device_detail
dev_err(&pdev->dev, "unable to enable the clk, "
"err = %d\n", err);
}
+
+ omap_rng_write(priv, RNG_INTMASK_REG, RNG_SHUTDOWN_OFLO_MASK);
}
return 0;
}