This is a note to let you know that I've just added the patch titled
hwrng: nomadik - keep clock enabled while hwrng is registered
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
hwrng-nomadik-keep-clock-enabled-while-hwrng-is-regi.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 5d5f2062573a5bb00f7b5eeff17391d2b35f50fd
Author: Martin Kaiser <martin@xxxxxxxxx>
Date: Sun Jul 2 19:35:02 2023 +0200
hwrng: nomadik - keep clock enabled while hwrng is registered
[ Upstream commit 039980de89dc9dd757418d6f296e4126cc3f86c3 ]
The nomadik driver uses devres to register itself with the hwrng core,
the driver will be unregistered from hwrng when its device goes out of
scope. This happens after the driver's remove function is called.
However, nomadik's clock is disabled in the remove function. There's a
short timeframe where nomadik is still registered with the hwrng core
although its clock is disabled. I suppose the clock must be active to
access the hardware and serve requests from the hwrng core.
Switch to devm_clk_get_enabled and let devres disable the clock and
unregister the hwrng. This avoids the race condition.
Fixes: 3e75241be808 ("hwrng: drivers - Use device-managed registration API")
Signed-off-by: Martin Kaiser <martin@xxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/char/hw_random/nomadik-rng.c b/drivers/char/hw_random/nomadik-rng.c
index e8f9621e79541..3774adf903a83 100644
--- a/drivers/char/hw_random/nomadik-rng.c
+++ b/drivers/char/hw_random/nomadik-rng.c
@@ -13,8 +13,6 @@
#include <linux/clk.h>
#include <linux/err.h>
-static struct clk *rng_clk;
-
static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
{
void __iomem *base = (void __iomem *)rng->priv;
@@ -36,21 +34,20 @@ static struct hwrng nmk_rng = {
static int nmk_rng_probe(struct amba_device *dev, const struct amba_id *id)
{
+ struct clk *rng_clk;
void __iomem *base;
int ret;
- rng_clk = devm_clk_get(&dev->dev, NULL);
+ rng_clk = devm_clk_get_enabled(&dev->dev, NULL);
if (IS_ERR(rng_clk)) {
dev_err(&dev->dev, "could not get rng clock\n");
ret = PTR_ERR(rng_clk);
return ret;
}
- clk_prepare_enable(rng_clk);
-
ret = amba_request_regions(dev, dev->dev.init_name);
if (ret)
- goto out_clk;
+ return ret;
ret = -ENOMEM;
base = devm_ioremap(&dev->dev, dev->res.start,
resource_size(&dev->res));
@@ -64,15 +61,12 @@ static int nmk_rng_probe(struct amba_device *dev, const struct amba_id *id)
out_release:
amba_release_regions(dev);
-out_clk:
- clk_disable_unprepare(rng_clk);
return ret;
}
static void nmk_rng_remove(struct amba_device *dev)
{
amba_release_regions(dev);
- clk_disable_unprepare(rng_clk);
}
static const struct amba_id nmk_rng_ids[] = {
