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.

I suspect nv_adma_register_mode failing may be the key. I don't know why 
this happens. It could be the timeout needs to be longer but I've tried 
increasing it significantly without apparent effect. (Essentially it's 
waiting for the status to go to the IDLE state, and then clears the GO 
bit and waits for LEGACY to be set. In this case both waits timed out.)