ath5k: fix spontaneus AR5312 freezes

commit 8bfae4f9938b6c1f033a5159febe97e441d6d526 upstream.

Sometimes while CPU have some load and ath5k doing the wireless
interface reset the whole WiSoC completely freezes. Set of tests shows
that using atomic delay function while we wait interface reset helps to
avoid such freezes.

The easiest way to reproduce this issue: create a station interface,
start continous scan with wpa_supplicant and load CPU by something. Or
just create multiple station interfaces and put them all in continous
scan.

This patch partially reverts the commit 1846ac3dbec0 ("ath5k: Use
usleep_range where possible"), which replaces initial udelay()
by usleep_range().

I do not know actual source of this issue, but all looks like that HW
freeze is caused by transaction on internal SoC bus, while wireless
block is in reset state.

Also I should note that I do not know how many chips are affected, but I
did not see this issue with chips, other than AR5312.

CC: Jiri Slaby <jirislaby@gmail.com>
CC: Nick Kossifidis <mickflemm@gmail.com>
CC: Luis R. Rodriguez <mcgrof@do-not-panic.com>
Fixes: 1846ac3dbec0 ("ath5k: Use usleep_range where possible")
Reported-by: Christophe Prevotaux <c.prevotaux@rural-networks.com>
Tested-by: Christophe Prevotaux <c.prevotaux@rural-networks.com>
Tested-by: Eric Bree <ebree@nltinc.com>
Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Zefan Li <lizefan@huawei.com>

diff --git a/drivers/net/wireless/ath/ath5k/reset.c b/drivers/net/wireless/ath/ath5k/reset.c
index 200f165c0c6d9c4a508ece1da7a2fd996b9df094..2cc3f4132550c76f859be893ca8ab04a4c2357b6 100644 (file)
--- a/drivers/net/wireless/ath/ath5k/reset.c
+++ b/drivers/net/wireless/ath/ath5k/reset.c
@@ -476,7 +476,7 @@ ath5k_hw_wisoc_reset(struct ath5k_hw *ah, u32 flags)
        regval = ioread32(reg);
        iowrite32(regval | val, reg);
        regval = ioread32(reg);
-       usleep_range(100, 150);
+       udelay(100);    /* NB: should be atomic */
 
        /* Bring BB/MAC out of reset */
        iowrite32(regval & ~val, reg);