From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bjorn Helgaas Subject: Re: 2.6.26-rc1 regression: ISA DMA broken (bisected) Date: Tue, 13 May 2008 10:59:32 -0600 Message-ID: <200805131059.32911.bjorn.helgaas@hp.com> References: <4823AAF2.7070102@keyaccess.nl> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from g5t0007.atlanta.hp.com (g5t0007.atlanta.hp.com [15.192.0.44]) by alsa0.perex.cz (Postfix) with ESMTP id 9C56C24B5A for ; Tue, 13 May 2008 19:01:06 +0200 (CEST) In-Reply-To: Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: Takashi Iwai Cc: ALSA devel , Rene Herman , Ingo Molnar , Linux Kernel , Glauber Costa , Thomas Gleixner , Pete Clements List-Id: alsa-devel@alsa-project.org On Friday 09 May 2008 12:06:55 am Takashi Iwai wrote: > Thanks for catching it. Yeah, the patch looks buggy. We had an > implicit assumption that dev = NULL for ISA devices that require 24bit > DMA. Naive question #1: Why don't we have a struct device for these ISA devices? PNP builds a struct device with DMA_24BIT_MASK for ISAPNP devices. Naive question #2: Do other architectures need similar fixes in dma_alloc_coherent()? > [PATCH] x86: Fix dma_alloc_coherent() for ISA devices > > The recent work on x86 dma_alloc_coherent() breaks the ISA DMA buffer > allocation, which is represented by "dev = NULL" and requires 24bit > DMA implicitly. > > Signed-off-by: Takashi Iwai > > --- > > diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c > index 0c37f16..c5ef1af 100644 > --- a/arch/x86/kernel/pci-dma.c > +++ b/arch/x86/kernel/pci-dma.c > @@ -385,11 +385,13 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle, > if (dma_alloc_from_coherent_mem(dev, size, dma_handle, &memory)) > return memory; > > - if (!dev) > + if (!dev) { > dev = &fallback_dev; > + gfp |= GFP_DMA; > + } > dma_mask = dev->coherent_dma_mask; > if (dma_mask == 0) > - dma_mask = DMA_32BIT_MASK; > + dma_mask = (gfp & GFP_DMA) ? DMA_24BIT_MASK : DMA_32BIT_MASK; > > /* Device not DMA able */ > if (dev->dma_mask == NULL) > @@ -403,7 +405,7 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle, > larger than 16MB and in this case we have a chance of > finding fitting memory in the next higher zone first. If > not retry with true GFP_DMA. -AK */ > - if (dma_mask <= DMA_32BIT_MASK) > + if (dma_mask <= DMA_32BIT_MASK && !(gfp & GFP_DMA)) > gfp |= GFP_DMA32; > #endif >