ath5k: fix spontaneus AR5312 freezes

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@44252 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/kernel/mac80211/patches/330-ath5k-fix-spontaneus-AR5312-freezes.patch

@@ -0,0 +1,45 @@
+From: Sergey Ryazanov <ryazanov.s.a@gmail.com>
+Date: Tue, 3 Feb 2015 22:37:26 +0300
+Subject: [PATCH] ath5k: fix spontaneus AR5312 freezes
+
+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>
+---
+--- a/drivers/net/wireless/ath/ath5k/reset.c
++++ b/drivers/net/wireless/ath/ath5k/reset.c
+@@ -478,7 +478,7 @@ ath5k_hw_wisoc_reset(struct ath5k_hw *ah
+ 	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);