netdev - Re: alchemy/gpr: au1000_eth regression with v2.6.37rc2

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Date:	Tue, 23 Nov 2010 16:01:37 +0100
From:	Wolfgang Grandegger <wg@...ndegger.com>
To:	Florian Fainelli <florian@...nwrt.org>
CC:	Linux-MIPS <linux-mips@...ux-mips.org>, Netdev@...r.kernel.org
Subject: Re: alchemy/gpr: au1000_eth regression with v2.6.37rc2

Hi Florian,

On 11/19/2010 11:46 AM, Florian Fainelli wrote:
> Hello Wolfgang,
> 
> On Friday 19 November 2010 11:29:45 Wolfgang Grandegger wrote:
>> Hello Florian,
>>
>> On 11/18/2010 11:30 PM, Florian Fainelli wrote:
>>> Hello Wolfgang,
>>>
>>> Le Thursday 18 November 2010 20:59:15, Wolfgang Grandegger a écrit :
>>>> Hello,
>>>>
>>>> I just realized that the v2.6.37-rc2 kernel does not boot any more on
>>>> the Alchemy GPR board. It works fine with v2.6.36. It hangs in the
>>>> probe function of the au1000_eth driver when probing the second
>>>>
>>>> ethernet port (eth1):
>>>>   au1000_eth_mii: probed
>>>>   au1000-eth au1000-eth.0: (unregistered net_device): attached PHY
>>>>   driver
>>>>
>>>> [Generic PHY] (mii_bus:phy_addr=0:00, irq=-1) au1000-eth au1000-eth.0:
>>>> eth0: Au1xx0 Ethernet found at 0x10500000, irq 35 au1000_eth: au1000_eth
>>>> version 1.7 Pete Popov <ppopov@...eddedalley.com> ... hangs ...
>>>>
>>>> Similar messages should follow for eth1. I narrowed down (bisect'ed) the
>>>>
>>>> problem to commit:
>>>>   commit d0e7cb5d401695809ba8c980124ab1d8c66efc8b
>>>>   Author: Florian Fainelli <florian@...nwrt.org>
>>>>   Date:   Wed Sep 8 11:15:13 2010 +0000
>>>>   
>>>>     au1000-eth: remove volatiles, switch to I/O accessors
>>>>     
>>>>     Remove all the volatile keywords where they were used, switch to
>>>>     using
>>>>
>>>> the proper readl/writel accessors.
>>>>
>>>>     Signed-off-by: Florian Fainelli <florian@...nwrt.org>
>>>>     Signed-off-by: David S. Miller <davem@...emloft.net>
>>>>
>>>> The kernel actually hangs when accessing "&aup->mac->mii_control" in
>>>> au1000_mdio_read(), but only for eth1. Any idea what does go wrong?
>>>
>>> I do not understand so far while it hangs only for eth1. My device only
>>> has one ethernet MAC, so I could not notice the problem. Looking at this
>>> close, there are a couple of u32 const* usages in
>>> au1000_mdio_{read,write} which are looking wrong to me now. Can you try
>>> to remove these?
>>
>> That did not help.
> 
> I suspected it, but thanks for the confirmation.
> 
>>
>>>> In principle, I do not want to access the MII regs of the MAC because
>>>> eth0 and eth1 are connected to switches. But that's not possible, even
>>>> with "aup->phy_static_config=1" and "aup->phy_addr=0".
>>>
>>> If you think this is another issue, I will fix it in another patch.
>>
>> Accessing the MII registers of the MAC should not hang the system even
>> if I do not need to. First I want to  understand why. Looks like a wired
>> optimizer issue.
> 
> I definitively agree, furthermore since there is a timeout for read and write 
> operations. I will look at the assembly and see if I can see anything 
> different.

The attached patch fixes the issue. It's caused by a simple porting
error. I'm going to prepare a proper patch later today.

Wolfgang.



View attachment "au1000-eth-mac-enable.patch" of type "text/x-diff" (1262 bytes)