Re: PCI memory reservation failures

Hello Alec,

Post/fwd this to the [email protected]. You'll get more 
replies there with people with more experience. 

	Luis

On Thu, May 06, 2004 at 07:45:41PM -0600, Alec H. Peterson wrote:
> Sorry for the crosspost, but this issue seems to have surfaced for users of 
> both of these drivers.  And yes I know this is not describing a problem 
> with either of the drivers represented on these lists, but hopefully people 
> will find it relevant.
> 
> I believe I have found a fix to these problems.  The root cause of the 
> problem is the fact that the BIOS in question is not aligning the memory it 
> is assigning to the CardBus slots.  So the kernel is attempting to align it 
> on its own, but then another problem comes up because in this case there is 
> only 8K of memory available, and that is how much some of the cards need 
> (in some cases they need even more).  According to the yenta driver the 
> minimum amount of memory that should be allocated to each slot is 16K. 
> Anyway, I have put a patch into drivers/pcmcia/yenta.c that looks like this 
> (in yenta_allocate_res(), kernel 2.4.25):
> 
>        start = config_readl(socket, offset) & mask;
>        end = config_readl(socket, offset+4) | ~mask;
> #if 1
>        if (!(type & IORESOURCE_IO) && (((end - start) < BRIDGE_SIZE_MIN) ||
>            (start & (end - start))))
>        {
>                printk(KERN_INFO "yenta %s: Preassigned resource start %lx 
> end %lx too small or not aligned.\n", socket->dev->slot_name, start, end);
>                res->start = res->end = 0;
>        }
>        else
> #endif
>        if (start && end > start) {
>                res->start = start;
> 
> Basically it is doing sanity checking on the memory that the PCI BIOS has 
> pre-allocated, and if the sanity check fails it goes ahead and allocates a 
> new block of memory (that happens automatically further along in 
> yenta_allocate_res()).  With this patch in place I can now initialize and 
> use both PrismGT and Atheros cards with no problems.
> 
> I welcome any feedback or input about this.  If this is good, bad, or an 
> abomination against the kernel I would really like to hear about it.  I've 
> sent it to the linux-kernel list as well (I received some helpful 
> suggestions there) but I have not yet had any feedback about whether or not 
> this is a good thing.  I don't have a huge variety of systems to test this 
> against so I would really love to hear how this works on other systems.
> 
> Thanks!
> 
> Alec
> 
> _______________________________________________
> Prism54-users mailing list
> [email protected]
> http://prism54.org/mailman/listinfo/prism54-users

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