linux-kernel - Re: sata_nv and 2.6.24 (was Re: fixed a bug of adma in rhel4u5 with HDS7250SASUN500G.)

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Message-ID: <4797ECF8.9000606@garzik.org>
Date:	Wed, 23 Jan 2008 20:42:16 -0500
From:	Jeff Garzik <jeff@...zik.org>
To:	Robert Hancock <hancockr@...w.ca>
CC:	Kuan Luo <kluo@...dia.com>, Tejun Heo <htejun@...il.com>,
	Mark Lord <liml@....ca>,
	IDE/ATA development list <linux-ide@...r.kernel.org>,
	Allen Martin <AMartin@...dia.com>,
	Peer Chen <pchen@...dia.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	David Milburn <dmilburn@...hat.com>
Subject: Re: sata_nv and 2.6.24 (was Re: fixed a bug of adma in rhel4u5 with
 HDS7250SASUN500G.)

Robert Hancock wrote:
> Jeff Garzik wrote:
>> Ping...  sata_nv status is still a bit open for 2.6.24, and I would 
>> like to move us forward a bit.
>>
>> * Kuan's patch...  it has been confirmed (and is needed), correct?  
>> can someone work up a good patch for 2.6.24?  The only one I ever 
>> received was badly word-wrapped, and at the time, Robert seemed 
>> uncertain of it, so I waited.
> 
> I can get you one later today hopefully.
> 
>>
>> * ADMA ATAPI 4GB issues...  playing tricks with the ordering of 
>> allocations and DMA masks is just way too fragile.  We just cannot 
>> guarantee that all allocators work that way.  The obvious solution to 
>> me seems to be hardcoding the consistent DMA mask to 32-bit, but using 
>> 64-bit for regular dma mask if-and-only-if ADMA is enabled.
> 
> That's not enough to fix the problem since there's issues with actual 
> transfer data being allocated above 4GB as well, not just the consistent 
>  allocations (it appears that blk_queue_bounce_limit setting to 32-bit 
> doesn't prevent this on x86_64). Either we play some funky games with 
> changing the DMA mask of the entire device to 32-bit if either port is 
> in ATAPI mode (which blew up when I tried it) or we add the ability to 
> set the DMA mask independently on each port (like by setting the mask on 
> the SCSI device and using that for DMA mapping instead) which requires 
> core changes.

Its all funky games that no other driver is doing...  There is one 
guaranteed to work scenario -- set all masks and bounce limits etc. to 
32-bit.  There is also one highly-likely-to-work scenario, disabling 
ADMA by default.


>> * it sure seems like there are other open sata_nv ADMA issues -- can 
>> we hard-confirm or deny this?  bugzilla wasn't very helpful for me.  
>> It doesn't seem like we can disable ADMA (to solve those issues) and 
>> get enough test time in (which is what I said a week (or more?) ago 
>> too...)
> 
> The NCQ/non-NCQ command switching issue is still hitting some people 
> (last I heard Kuan was looking into this), also there's a hotplug issue 
> that Tejun reported..

The former implies we need to disable swncq for 2.6.24, if it's not 
stable yet.

	Jeff


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