Re: [discuss] Re: 32-bit dma allocations on 64-bit platforms

[Takashi Iwai <tiwai@suse.de>]

At Thu, 24 Jun 2004 20:44:47 +0200,
Andrea Arcangeli wrote:
> 
> On Thu, Jun 24, 2004 at 08:33:02PM +0200, Takashi Iwai wrote:
> > Sure, in extreme cases, it can't work.  But at least, it _may_ work
> > better than using only GFP_DMA.  And indeed it should (still) work
> > on most of consumer PC boxes.  The addition of another zone would help
> > much better, though.
> 
> of course agreed.

The below is the new patch to follow your advice.


thanks,

Takashi

--- linux-2.6.7/arch/i386/kernel/pci-dma.c-dist	2004-06-24 15:56:46.017473544 +0200
+++ linux-2.6.7/arch/i386/kernel/pci-dma.c	2004-06-25 17:43:42.509366917 +0200
@@ -23,11 +23,22 @@ void *dma_alloc_coherent(struct device *
 	if (dev == NULL || (dev->coherent_dma_mask < 0xffffffff))
 		gfp |= GFP_DMA;
 
+ again:
 	ret = (void *)__get_free_pages(gfp, get_order(size));
 
-	if (ret != NULL) {
+	if (ret == NULL) {
+		if (dev && (gfp & GFP_DMA)) {
+			gfp &= ~GFP_DMA;
+			goto again;
+		}
+	} else {
 		memset(ret, 0, size);
 		*dma_handle = virt_to_phys(ret);
+		if (!(gfp & GFP_DMA) &&
+		    (((unsigned long)*dma_handle + size - 1) & ~(unsigned long)dev->coherent_dma_mask)) {
+			free_pages((unsigned long)ret, get_order(size));
+			return NULL;
+		}
 	}
 	return ret;
 }