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From: nschichan@freebox.fr (Nicolas Schichan)
To: linux-arm-kernel@lists.infradead.org
Subject: Spurious timeouts in mvmdio
Date: Mon, 02 Dec 2013 16:15:54 +0100	[thread overview]
Message-ID: <529CA42A.3040504@freebox.fr> (raw)


Hi,

During 3.13-rc1 testing, I have found out that the mvmdio driver would report 
timeouts on the kernel console:

[   11.011334] orion-mdio orion-mdio: Timeout: SMI busy for too long

The hardware is a MV88F6281 Kirkwood CPU. The mvmdio driver is using the irq 
line 46 (ge00_err).

I am inclined to believe that it is due to the fact that wait_event_timeout() 
is called with a timeout parameter of 1 jiffy in orion_mdio_wait_ready(). If 
the timer interrupt ticks right after calling wait_event_timeout(), we may end 
up spending much less time than MVMDIO_SMI_TIMEOUT (1 msec) in 
wait_event_timeout(), and as a result report a timeout as the MDIO access did 
not complete in such a short time.

As to how to fix this, I see two options (I don't know which one would be 
prefered):

- Option 1: always pass a timeout of at least 2 jiffy to wait_event_timeout().
- Option 2: switch to wait_event_hrtimeout().

I can provide patches for both options.

Regards,

-- 
Nicolas Schichan

WARNING: multiple messages have this Message-ID (diff)
From: Nicolas Schichan <nschichan@freebox.fr>
To: LKML <linux-kernel@vger.kernel.org>,
	netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Cc: "David S. Miller" <davem@davemloft.net>,
	Florian Fainelli <florian@openwrt.org>,
	Leigh Brown <leigh@solinno.co.uk>,
	Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Subject: Spurious timeouts in mvmdio
Date: Mon, 02 Dec 2013 16:15:54 +0100	[thread overview]
Message-ID: <529CA42A.3040504@freebox.fr> (raw)


Hi,

During 3.13-rc1 testing, I have found out that the mvmdio driver would report 
timeouts on the kernel console:

[   11.011334] orion-mdio orion-mdio: Timeout: SMI busy for too long

The hardware is a MV88F6281 Kirkwood CPU. The mvmdio driver is using the irq 
line 46 (ge00_err).

I am inclined to believe that it is due to the fact that wait_event_timeout() 
is called with a timeout parameter of 1 jiffy in orion_mdio_wait_ready(). If 
the timer interrupt ticks right after calling wait_event_timeout(), we may end 
up spending much less time than MVMDIO_SMI_TIMEOUT (1 msec) in 
wait_event_timeout(), and as a result report a timeout as the MDIO access did 
not complete in such a short time.

As to how to fix this, I see two options (I don't know which one would be 
prefered):

- Option 1: always pass a timeout of at least 2 jiffy to wait_event_timeout().
- Option 2: switch to wait_event_hrtimeout().

I can provide patches for both options.

Regards,

-- 
Nicolas Schichan

             reply	other threads:[~2013-12-02 15:15 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-12-02 15:15 Nicolas Schichan [this message]
2013-12-02 15:15 ` Spurious timeouts in mvmdio Nicolas Schichan
2013-12-03 12:23 ` Jason Cooper
2013-12-03 12:23   ` Jason Cooper
2013-12-03 12:40   ` Russell King - ARM Linux
2013-12-03 12:40     ` Russell King - ARM Linux
2013-12-03 13:43     ` Jason Cooper
2013-12-03 13:43       ` Jason Cooper
2013-12-03 18:48       ` Nicolas Schichan
2013-12-03 18:48         ` Nicolas Schichan
2013-12-03 20:57     ` Leigh Brown
2013-12-03 20:57       ` Leigh Brown
2013-12-03 22:45       ` Sebastian Hesselbarth
2013-12-03 22:45         ` Sebastian Hesselbarth
2013-12-03 23:20         ` Leigh Brown
2013-12-03 23:20           ` Leigh Brown
2013-12-03 23:17           ` Sebastian Hesselbarth
2013-12-03 23:17             ` Sebastian Hesselbarth
2013-12-03 23:38             ` Leigh Brown
2013-12-03 23:38               ` Leigh Brown
2013-12-03 23:42               ` Russell King - ARM Linux
2013-12-03 23:42                 ` Russell King - ARM Linux
2013-12-04 11:40                 ` Nicolas Schichan
2013-12-04 11:40                   ` Nicolas Schichan
2013-12-16 18:07                 ` Nicolas Schichan
2013-12-16 18:07                   ` Nicolas Schichan
2013-12-16 18:28                   ` Leigh Brown
2013-12-16 18:28                     ` Leigh Brown
2013-12-17 13:49                     ` Nicolas Schichan
2013-12-17 13:49                       ` Nicolas Schichan
2013-12-16 18:48                   ` Russell King - ARM Linux
2013-12-16 18:48                     ` Russell King - ARM Linux
2013-12-03 23:45               ` Sebastian Hesselbarth
2013-12-03 23:45                 ` Sebastian Hesselbarth
2013-12-03 23:45                 ` Sebastian Hesselbarth
2013-12-03 13:16   ` [PATCH] net: mvmdio: fix wait_event_timeout() being called with a 1 jiffy timeout Nicolas Schichan
2013-12-03 13:16     ` Nicolas Schichan
2013-12-03 13:34     ` Russell King - ARM Linux
2013-12-03 13:34       ` Russell King - ARM Linux

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