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ath9k: Fix softlockup in AR9485(backported)

PATCH New Mohammed Shafi Shajakhan 2 participants 3 messages Jun 13, 2012 – Jun 14, 2012 Qualcomm Atheros ATH9K wireless driver

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Mohammed Shafi Shajakhan

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#0 lore raw

PATCH 1/1 ath9k: Fix softlockup in AR9485(backported)

From: Mohammed Shafi Shajakhan <[email protected]>

Please note this is the backported version for the linux stable tree, while the patch for wireless-testing tree
http://permalink.gmane.org/gmane.linux.kernel.wireless.general/92608

steps to recreate:
load latest ath9k driver with AR9485
stop the network-manager and wpa_supplicant
bring the interface up

	Call Trace:
	[<ffffffffa0517490>] ? ath_hw_check+0xe0/0xe0 [ath9k]
	[<ffffffff812cd1e8>] __const_udelay+0x28/0x30
	[<ffffffffa03bae7a>] ar9003_get_pll_sqsum_dvc+0x4a/0x80 [ath9k_hw]
	[<ffffffffa05174eb>] ath_hw_pll_work+0x5b/0xe0 [ath9k]
	[<ffffffff810744fe>] process_one_work+0x11e/0x470
	[<ffffffff8107530f>] worker_thread+0x15f/0x360
	[<ffffffff810751b0>] ? manage_workers+0x230/0x230
	[<ffffffff81079af3>] kthread+0x93/0xa0
	[<ffffffff815fd3a4>] kernel_thread_helper+0x4/0x10
	[<ffffffff81079a60>] ? kthread_freezable_should_stop+0x70/0x70
	[<ffffffff815fd3a0>] ? gs_change+0x13/0x13

ensure that the PLL-WAR for AR9485/AR9340 is executed only if the STA is associated (or) IBSS/AP mode had started beaconing. Ideally this WAR is needed to recover from some rare beacon stuck during stress testing. Before the STA is associated/IBSS had started beaconing, PLL4(0x1618c) always seem to have zero even though we had configured PLL3(0x16188) to query about PLL's locking status. When we keep on polling infinitely PLL4's 8th bit(ie check for PLL locking measurements is done), machine hangs due to softlockup.

fixes https://bugzilla.redhat.com/show_bug.cgi?id=811142

Reported-by Rolf Offermanns <[email protected]>
Cc stable at vger.kernel.org [3.0+]
Tested-by Mohammed Shafi Shajakhan <[email protected]>
Signed-off-by Mohammed Shafi Shajakhan <[email protected]>
---
 drivers/net/wireless/ath/ath9k/main.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)
drivers/net/wireless/ath/ath9k/main.c +9 -0
index 4de4473..41096f6 100644
@@ -971,6 +971,15 @@ void ath_hw_pll_work(struct work_struct *work)
 					    hw_pll_work.work);
 	u32 pll_sqsum;
 
+	/*
+	 * ensure that the PLL WAR is executed only
+	 * after the STA is associated (or) if the
+	 * beaconing had started in interfaces that
+	 * uses beacons.
+	 */
+	if (!(sc->sc_flags & SC_OP_BEACONS))
+		return;
+
 	if (AR_SREV_9485(sc->sc_ah)) {
 
 		ath9k_ps_wakeup(sc);
Signature · 1 line
1.7.4.1
#1 lore raw

PATCH 1/1 ath9k: Fix softlockup in AR9485(backported)

Quoted 24 lines · Mohammed Shafi Shajakhan

From: Mohammed Shafi Shajakhan <[email protected]>

Please note this is the backported version for the linux stable tree, while the patch for wireless-testing tree
http://permalink.gmane.org/gmane.linux.kernel.wireless.general/92608

steps to recreate:
load latest ath9k driver with AR9485
stop the network-manager and wpa_supplicant
bring the interface up

	Call Trace:
	[<ffffffffa0517490>] ? ath_hw_check+0xe0/0xe0 [ath9k]
	[<ffffffff812cd1e8>] __const_udelay+0x28/0x30
	[<ffffffffa03bae7a>] ar9003_get_pll_sqsum_dvc+0x4a/0x80 [ath9k_hw]
	[<ffffffffa05174eb>] ath_hw_pll_work+0x5b/0xe0 [ath9k]
	[<ffffffff810744fe>] process_one_work+0x11e/0x470
	[<ffffffff8107530f>] worker_thread+0x15f/0x360
	[<ffffffff810751b0>] ? manage_workers+0x230/0x230
	[<ffffffff81079af3>] kthread+0x93/0xa0
	[<ffffffff815fd3a4>] kernel_thread_helper+0x4/0x10
	[<ffffffff81079a60>] ? kthread_freezable_should_stop+0x70/0x70
	[<ffffffff815fd3a0>] ? gs_change+0x13/0x13
Quoted 8 lines

ensure that the PLL-WAR for AR9485/AR9340 is executed only if the STA is associated (or) IBSS/AP mode had started beaconing. Ideally this WAR is needed to recover from some rare beacon stuck during stress testing. Before the STA is associated/IBSS had started beaconing, PLL4(0x1618c) always seem to have zero even though we had configured PLL3(0x16188) to query about PLL's locking status. When we keep on polling infinitely PLL4's 8th bit(ie check for PLL locking measurements is done), machine hangs due to softlockup.

While I do agree that this patch fixes the regression for AR9485 chipsets, the code in ar9003_get_pll_sqsum_dvc needs to be fixed, i.e., to not loop till the end of time and have a timeout.

Sujith

author
#2 lore raw

PATCH 1/1 ath9k: Fix softlockup in AR9485(backported)

Hi Sujith,

Quoted 34 lines · Sujith Manoharan
Quoted 24 lines · Mohammed Shafi Shajakhan

From: Mohammed Shafi Shajakhan<[email protected]>

Please note this is the backported version for the linux stable tree, while the patch for wireless-testing tree
http://permalink.gmane.org/gmane.linux.kernel.wireless.general/92608

steps to recreate:
load latest ath9k driver with AR9485
stop the network-manager and wpa_supplicant
bring the interface up

	Call Trace:
	[<ffffffffa0517490>] ? ath_hw_check+0xe0/0xe0 [ath9k]
	[<ffffffff812cd1e8>] __const_udelay+0x28/0x30
	[<ffffffffa03bae7a>] ar9003_get_pll_sqsum_dvc+0x4a/0x80 [ath9k_hw]
	[<ffffffffa05174eb>] ath_hw_pll_work+0x5b/0xe0 [ath9k]
	[<ffffffff810744fe>] process_one_work+0x11e/0x470
	[<ffffffff8107530f>] worker_thread+0x15f/0x360
	[<ffffffff810751b0>] ? manage_workers+0x230/0x230
	[<ffffffff81079af3>] kthread+0x93/0xa0
	[<ffffffff815fd3a4>] kernel_thread_helper+0x4/0x10
	[<ffffffff81079a60>] ? kthread_freezable_should_stop+0x70/0x70
	[<ffffffff815fd3a0>] ? gs_change+0x13/0x13
Quoted 8 lines

ensure that the PLL-WAR for AR9485/AR9340 is executed only if the STA is associated (or) IBSS/AP mode had started beaconing. Ideally this WAR is needed to recover from some rare beacon stuck during stress testing. Before the STA is associated/IBSS had started beaconing, PLL4(0x1618c) always seem to have zero even though we had configured PLL3(0x16188) to query about PLL's locking status. When we keep on polling infinitely PLL4's 8th bit(ie check for PLL locking measurements is done), machine hangs due to softlockup.

Quoted 4 lines

While I do agree that this patch fixes the regression for AR9485 chipsets, the code in ar9003_get_pll_sqsum_dvc needs to be fixed, i.e., to not loop till the end of time and have a timeout.

agreed, i already have a patch for that and did some tests too :)

(quoted diff) +0 -0

b/drivers/net/wireless/ath/ath9k/hw.c
index 6fa8128..932199c 100644

drivers/net/wireless/ath/ath9k/hw.c +14 -1
@@ -719,13 +719,26 @@ static void ath9k_hw_init_qos(struct ath_hw *ah)
 
  u32 ar9003_get_pll_sqsum_dvc(struct ath_hw *ah)
  {
+       int i = 0;
+       struct ath_common *common = ath9k_hw_common(ah);
+
         REG_CLR_BIT(ah, PLL3, PLL3_DO_MEAS_MASK);
         udelay(100);
         REG_SET_BIT(ah, PLL3, PLL3_DO_MEAS_MASK);
 
-       while ((REG_READ(ah, PLL4) & PLL4_MEAS_DONE) == 0)
+       while ((REG_READ(ah, PLL4) & PLL4_MEAS_DONE) == 0) {
+
+               i++;
                 udelay(100);
 
+               if (i > 100) {
+                       ath_err(common, "PLL4 meaurement not done");
+                       WARN_ON(1);
+                       break;
+               }
+
+       }
+
         return (REG_READ(ah, PLL3) & SQSUM_DVC_MASK) >> 3;
  }
  EXPORT_SYMBOL(ar9003_get_pll_sqsum_dvc);

during my testing i found that, when things are fine we would usually break out when i = 2. will send this patch too. thanks for your thoughts!

Signature · 2 lines
thanks,
shafi