linux-kernel - Re: [PATCH] sata_nv: fix ADMA ATAPI issues with memory over 4GB (v2)

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Date:	Thu, 22 Nov 2007 19:01:39 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	Tejun Heo <htejun@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	ide <linux-ide@...r.kernel.org>, Jeff Garzik <jeff@...zik.org>
Subject: Re: [PATCH] sata_nv: fix ADMA ATAPI issues with memory over 4GB (v2)

Tejun Heo wrote:
> Hello, Robert.
> 
> Robert Hancock wrote:
>> This fixes some problems with ATAPI devices on nForce4 controllers in ADMA
>> mode on systems with memory located above 4GB. We need to delay setting the
>> 64-bit DMA mask until the PRD table and padding buffer are allocated so that
>> they don't get allocated above 4GB and break legacy mode (which is needed for
>> ATAPI devices). Also, explicitly set a 32-bit DMA mask before allocating the
>> legacy buffers since setting the DMA mask affects both ports and we need to
>> ensure the second port's buffers are allocated properly (fixes a problem
>> with the previous version of this patch).
>>
>> Signed-off-by: Robert Hancock <hancockr@...w.ca>
>>
>> +	/* Ensure DMA mask is set to 32-bit before allocating legacy PRD and
>> +	   pad buffers */
>> +	pci_set_dma_mask(pdev, DMA_BIT_MASK(32));
>> +	pci_set_consistent_dma_mask(pdev, DMA_BIT_MASK(32));
> [--snip--]
>> +	pci_set_dma_mask(pdev, DMA_BIT_MASK(64));
>> +	pci_set_consistent_dma_mask(pdev, DMA_BIT_MASK(64));
> 
> I'm probably being paranoid here but please add error checks.  Just
> checking return value and returning error suffices.

In the 32-bit case, I'm pretty sure those are guaranteed not to fail 
because 32-bit is the default. For the 64-bit ones, we don't care if 
they fail, because then we'll just use whatever mask ends up being set 
(we store the actual set DMA mask in adma_dma_mask for use when we need 
to reconfigure the bounce limit). We definitely don't want to fail 
initialization if the 64-bit set doesn't succeed..
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