Subject: Re: [atl1-devel] [PATCH 2/2] atl1: wrap problematic optimizations in CONFIG_ATL1_EXPERIMENTAL

From: Chris Snook <[email-masked]>
Date: Fri, 07 Sep 2007 20:27:31 -0400

Luca wrote:
> On 9/8/07, Chris Snook <[email-masked]> wrote:
>> From: Chris Snook <[email-masked]>
>>
>> Make certain problematic optimizations build-time configurable.
>>
>> Signed-off-by: Chris Snook <[email-masked]>
>> Acked-by: Jay Cliburn <[email-masked]>
>>
>> --- a/drivers/net/atl1/atl1_main.c      2007-09-04 10:12:38.000000000 -0400
>> +++ b/drivers/net/atl1/atl1_main.c      2007-09-04 11:23:26.000000000 -0400
>> @@ -2203,22 +2203,26 @@ static int __devinit atl1_probe(struct p
>>         struct net_device *netdev;
>>         struct atl1_adapter *adapter;
>>         static int cards_found = 0;
>> -       bool pci_using_64 = true;
>> +       bool pci_using_64 = false;
>>         int err;
>>
>>         err = pci_enable_device(pdev);
>>         if (err)
>>                 return err;
>>
>> +#ifdef CONFIG_ATL1_EXPERIMENTAL
>>         err = pci_set_dma_mask(pdev, DMA_64BIT_MASK);
>> +       if (!err) {
>> +               pci_using_64 = true;
>> +               goto dma_ok;
>> +       }
>> +#endif /* CONFIG_ATL1_EXPERIMENTAL */
> 
> This is more like CONFIG_ATL1_PLEASE_KILL_MY_MACHINE; I really don't
> see the problem with just limiting the DMA mask:
> - if you don't have physical mem over the 4GB boundary limiting DMA
> doesn't make any difference
> - if you have more than 4GB of memory the machine won't survive long without it

Atheros is still working on this, and we plan to fix it.  64-bit DMA *should* 
work.  I just resubmitted your patch with the comment Jeff requested.  I still 
may want to revisit CONFIG_ATL1_EXPERIMENTAL soon when I start playing around 
with more features.

	-- Chris