Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933423Ab1ESP4P (ORCPT ); Thu, 19 May 2011 11:56:15 -0400 Received: from smtprelay06.ispgateway.de ([80.67.31.104]:58776 "EHLO smtprelay06.ispgateway.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754146Ab1ESP4O (ORCPT ); Thu, 19 May 2011 11:56:14 -0400 Message-ID: <4DD53E2B.2090002@ladisch.de> Date: Thu, 19 May 2011 17:58:35 +0200 From: Clemens Ladisch User-Agent: Thunderbird 2.0.0.24 (Windows/20100228) MIME-Version: 1.0 To: Konrad Rzeszutek Wilk , Leon Woestenberg CC: linux-pci@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: mmap() implementation for pci_alloc_consistent() memory? References: <20110519145921.GE9854@dumpdata.com> In-Reply-To: <20110519145921.GE9854@dumpdata.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Df-Sender: linux-kernel@cl.domainfactory-kunde.de Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3961 Lines: 116 Konrad Rzeszutek Wilk wrote: > On Thu, May 19, 2011 at 12:14:40AM +0200, Leon Woestenberg wrote: > > I cannot get my driver's mmap() to work. I allocate 64 KiB ringbuffer > > using pci_alloc_consistent(), then implement mmap() to allow programs > > to map that memory into their user space. > > ... > > int ringbuffer_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf) > > { > > /* the buffer allocated with pci_alloc_consistent() */ > > void *vaddr = ringbuffer_virt; > > int ret; > > > > /* find the struct page that describes vaddr, the buffer > > * allocated with pci_alloc_consistent() */ > > struct page *page = virt_to_page(lro_char->engine->ringbuffer_virt); > > vmf->page = page; > > > > /*** I have verified that vaddr, page, and the pfn correspond with vaddr = pci_alloc_consistent() ***/ > > ret = vm_insert_pfn(vma, address, page_to_pfn(page)); > > address is the vmf->virtual_address? > > And is the page_to_pfn(page) value correct? As in: > > int pfn = page_to_pfn(page); > > WARN(pfn << PAGE_SIZE != vaddr,"Something fishy."); > > Hm, I think I might have misled you now that I look at that WARN. > > The pfn to be supplied has to be physical page frame number. Which in > this case should be your bus addr shifted by PAGE_SIZE. Duh! Try that > value. There are wildly different implementations of pci_alloc_consistent (actually dma_alloc_coherent) that can return somewhat different virtual and/or physical addresses. > I think a better example might be the 'hpet_mmap' code Which is x86 and ia64 only. > > static int ringbuffer_mmap(struct file *file, struct vm_area_struct *vma) > > { > > vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); So is this an architecture without coherent caches? Or would you want to use pgprot_dmacoherent, if available? I recently looked into this problem, and ended up with the code below. I then decided that streaming DMA mappings might be a better idea. Regards, Clemens /* returns the struct page from the result of dma_alloc_coherent() */ struct page *dma_coherent_page(struct device *device, void *address, dma_addr_t bus) { #if defined(CONFIG_ALPHA) || \ defined(CONFIG_CRIS) || \ defined(CONFIG_IA64) || \ defined(CONFIG_MIPS) || \ (defined(CONFIG_PPC) && !defined(CONFIG_NOT_COHERENT_CACHE)) || \ defined(CONFIG_SPARC64) || \ defined(CONFIG_TILE) || \ defined(CONFIG_UNICORE32) || \ defined(CONFIG_X86) #ifdef CONFIG_MIPS if (!plat_device_is_coherent(device)) address = CAC_ADDR(address); #endif return virt_to_page(address); #elif defined(CONFIG_ARM) return pfn_to_page(dma_to_pfn(device, bus)); #elif defined(CONFIG_FRV) || \ defined(CONFIG_MN10300) #ifdef CONFIG_MN10300 if (WARN(!IS_ALIGNED(bus, PAGE_SIZE)), "PCI SRAM allocator is broken\n") return NULL; #endif return virt_to_page(bus_to_virt(bus)); #elif defined(CONFIG_M68K) || \ defined(CONFIG_SPARC32) return virt_to_page(phys_to_virt(bus)); #elif defined(CONFIG_PARISC) return virt_to_page(__va(bus)); #elif defined(CONFIG_SUPERH) return pfn_to_page(bus >> PAGE_SHIFT); #elif defined(CONFIG_MICROBLAZE) || \ (defined(CONFIG_PPC) && defined(CONFIG_NOT_COHERENT_CACHE)) unsigned long vaddr = (unsigned long)address; pgd_t *pgd = pgd_offset_k(vaddr); pud_t *pud = pud_offset(pgd, vaddr); pmd_t *pmd = pmd_offset(pud, vaddr); pte_t *pte = pte_offset_kernel(pmd, vaddr); if (!pte_none(*pte) && pte_present(*pte)) { unsigned long pfn = pte_pfn(*pte); if (pfn_valid(pfn)) return pfn_to_page(pfn); } return NULL; #elif defined(CONFIG_XTENSA) #error non-cacheable remapping not implemented #else #error unknown architecture #endif } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/