Re: [PATCH] sata_nv: fix nmi intr or system hanging in rhel4u6 adma.

[Robert Hancock <hancockr@shaw.ca>]

Kuan Luo wrote:
> Jeff wrote:
>> robert worte:
>>> This is basically avoiding switching into register mode, 
>> right? I don't 
>>> think this is a very good solution as the point of the 
>> tf_read function 
>>> is that it's supposed to read the taskfile provided by the drive to 
>>> diagnose the error, so not doing this isn't a good thing.
>> Agree with this analysis -- if ->tf_read() is being called, then 
>> obviously the core wants a current copy of the device's ATA registers.
>>
>> It is not a good solution to simply avoiding returning 
>> meaningful data, 
>> because -- as Robert notes -- we need tf_read for analysis.
>>
>> 	Jeff
>>
> 
> The driver got one error : "nv_adma_check_cpb: CPB 0, flags=0x11". The
> code entered ata_port_abort -> ata_qc_complete
> -> fill_result_tf->nv_adma_tf_read.
> 
> Firstly, nv_adma_register_mode failed, showing the below messages:
> timeout waiting for ADMA IDLE, stat=0x440
> timeout waiting for ADMA LEGACY, stat=0x440
> 
> Then enter ata_tf_read function. 
> I found the system hung at tf->hob_nsect = ioread8(ioaddr->nsect_addr);
> Sometimes the screen showed "
> CPU0: Machin check Exception 0000000000000004
> Bank 4:b200000000070f0f
> kernel panic -not syncing: CPU Context corrupt.
> "
> If nv_adma_register_mode failed, the reg result should be not
> meaningful. 
> I don't know why the systm hung.

By the way, this MCE indicates that the CPU integrated northbridge got a 
watchdog error indicating that a bus transaction timed out (presumably 
on the HyperTransport link). This likely indicates that the chipset 
failed to respond to a CPU read of that register. Obviously this is 
something we want to avoid causing..