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Date:	Fri, 21 Nov 2008 09:47:55 -0800
From:	David Daney <ddaney@caviumnetworks.com>
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To:	Sergei Shtylyov <sshtylyov@ru.mvista.com>
CC:	Alan Cox <alan@lxorguk.ukuu.org.uk>, linux-ide@vger.kernel.org,
	linux-mips <linux-mips@linux-mips.org>
Subject: Re: [PATCH] ide: New libata driver for OCTEON SOC Compact Flash interface.
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Sergei Shtylyov wrote:
> David Daney wrote:
[...]
> 
>>> What stops the following occuring
> 
>>>     ATA irq
>>>         BUSY still set
>>>         Queue tasklet
> 
>>>     Other irq on same line
>>>     ATA busy clear
>>>         Handle command
> 
>    Is CF interrupt indeed shared with anything?
> 
>>>     Tasklet runs but command was sorted out
> 
>>> (or a reset of the ata controller in the gap)
> 
>> Probably nothing.  I will try to sort it out.
> 
>    It's the need for the tasklet that seems doubtful to me...
> 

The interrupt occurs *before* the device de-asserts BUSY.  A small pause 
is needed to allow the device to clear BUSY and allow libata to function 
normally.

Calling ata_sff_host_intr() while BUSY is asserted causes the driver to 
fail, as it is expecting to be called from a true IDE interrupt routine. 
  Delaying calling ata_sff_host_intr() until BUSY is clear (using the 
tasklet) seemed to be the cleanest way to write the driver given that we 
are using an interrupt generated by DMA complete.

David Daney.