Re: [PATCH] libata-pmp: clear hob for pmp register accesses

[Tejun Heo <htejun@gmail.com>]

Mark Lord wrote:
> Mark Lord wrote:
>> Tejun Heo wrote:
>>> Hello, Mark.
>>>
>>> Mark Lord wrote:
>>>> Tejun, I've added PMP to sata_mv, and am now trying to get it
>>>> to work with a Marvell PM attached.
>>>>
>>>> And the behaviour I see is very bizarre.
>>>>
>>>> After hard+soft resets, the PM signature is found,
>>>> and libata interrogates the PM registers.
>>>>
>>>> It successfully reads register 0, and then register 1.
>>>> But all subsequent registers read out (incorrectly) as zeros.
> ..
> 
> Saeed has confirmed this behaviour with a SATA analyzer.
> The Marvell port-multiplier apparently likes to see clean HOB
> information when accessing PMP registers.
> 
> Since sata_mv uses PIO shadow register access, this doesn't happen
> automatically, as it might in a more purely FIS-based driver (eg. ahci).
> 
> One way to fix this is to flag these commands with ATA_TFLAG_LBA48,
> forcing libata to write out the HOB fields with known (zero) values.
> 
> Signed-off-by: Saeed Bishara <saeed@marvell.com>
> Acked-by: Mark Lord <mlord@pobox.com>

Acked-by: Tejun Heo <htejun@gmail.com>

I think this is correct w/ or w/o the mv problem.

-- 
tejun