linux-kernel - [PATCH] x86: adjust GFP mask handling for coherent allocations (take 2)

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Date:	Wed, 04 Nov 2009 12:28:39 +0000
From:	"Jan Beulich" <JBeulich@...ell.com>
To:	<mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc:	"Takashi Iwai" <tiwai@...e.de>, <linux-kernel@...r.kernel.org>,
	<jbarnes@...tuousgeek.org>
Subject: [PATCH] x86: adjust GFP mask handling for coherent allocations
	 (take 2)

Rather than forcing GFP flags and DMA mask to be inconsistent, GFP
flags should be determined even for the fallback device through
dma_alloc_coherent_mask()/dma_alloc_coherent_gfp_flags(). This
restores 64-bit behavior as it was prior to commits
8965eb19386fdf5ccd0ef8b02593eb8560aa3416 and
4a367f3a9dbf2e7ffcee4702203479809236ee6e (not sure why there are two of
them), where GFP_DMA was forced on for 32-bit, but not for 64-bit, with
the slight adjustment that afaict even 32-bit doesn't need this without
CONFIG_ISA.

Signed-off-by: Jan Beulich <jbeulich@...ell.com>
Cc: Takashi Iwai <tiwai@...e.de>
Cc: Jesse Barnes <jbarnes@...tuousgeek.org>

---
 arch/x86/include/asm/dma-mapping.h |   10 +++++++---
 arch/x86/kernel/pci-dma.c          |    6 ++----
 2 files changed, 9 insertions(+), 7 deletions(-)

--- linux-2.6.32-rc6/arch/x86/include/asm/dma-mapping.h	2009-11-04 13:23:36.000000000 +0100
+++ 2.6.32-rc6-x86-dma-mask-gfp/arch/x86/include/asm/dma-mapping.h	2009-10-27 11:10:28.000000000 +0100
@@ -14,6 +14,12 @@
 #include <asm/swiotlb.h>
 #include <asm-generic/dma-coherent.h>
 
+#ifdef CONFIG_ISA
+#define ISA_DMA_BIT_MASK DMA_BIT_MASK(24)
+#else
+#define ISA_DMA_BIT_MASK DMA_BIT_MASK(32)
+#endif
+
 extern dma_addr_t bad_dma_address;
 extern int iommu_merge;
 extern struct device x86_dma_fallback_dev;
@@ -124,10 +130,8 @@ dma_alloc_coherent(struct device *dev, s
 	if (dma_alloc_from_coherent(dev, size, dma_handle, &memory))
 		return memory;
 
-	if (!dev) {
+	if (!dev)
 		dev = &x86_dma_fallback_dev;
-		gfp |= GFP_DMA;
-	}
 
 	if (!is_device_dma_capable(dev))
 		return NULL;
--- linux-2.6.32-rc6/arch/x86/kernel/pci-dma.c	2009-11-04 13:23:36.000000000 +0100
+++ 2.6.32-rc6-x86-dma-mask-gfp/arch/x86/kernel/pci-dma.c	2009-10-27 11:14:11.000000000 +0100
@@ -45,12 +45,10 @@ int iommu_pass_through __read_mostly;
 dma_addr_t bad_dma_address __read_mostly = 0;
 EXPORT_SYMBOL(bad_dma_address);
 
-/* Dummy device used for NULL arguments (normally ISA). Better would
-   be probably a smaller DMA mask, but this is bug-to-bug compatible
-   to older i386. */
+/* Dummy device used for NULL arguments (normally ISA). */
 struct device x86_dma_fallback_dev = {
 	.init_name = "fallback device",
-	.coherent_dma_mask = DMA_BIT_MASK(32),
+	.coherent_dma_mask = ISA_DMA_BIT_MASK,
 	.dma_mask = &x86_dma_fallback_dev.coherent_dma_mask,
 };
 EXPORT_SYMBOL(x86_dma_fallback_dev);



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