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

["Kuan Luo" <kluo@nvidia.com>]

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.
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