From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id C13BC8D003B for ; Tue, 24 May 2011 10:18:16 -0400 (EDT) Received: by bwz17 with SMTP id 17so8410706bwz.14 for ; Tue, 24 May 2011 07:18:11 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <4DDA1B18.3080201@ladisch.de> References: <20110519145921.GE9854@dumpdata.com> <4DD53E2B.2090002@ladisch.de> <4DD60F57.8030000@ladisch.de> <4DDA1B18.3080201@ladisch.de> Date: Tue, 24 May 2011 16:18:11 +0200 Message-ID: Subject: Re: mmap() implementation for pci_alloc_consistent() memory? From: Leon Woestenberg Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Clemens Ladisch Cc: Takashi Iwai , Konrad Rzeszutek Wilk , linux-pci@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Hello Clemens, On Mon, May 23, 2011 at 10:30 AM, Clemens Ladisch wrote: > Leon Woestenberg wrote: >> Having dma_mmap_coherent() there is good for one or two archs, but how >> can we built portable drivers if the others arch's are still missing? > > Easy: Resolve all issues, implement it for all the other arches, and add > it to the official DMA API. > >> How would dma_mmap_coherent() look like on x86? > > X86 and some others are always coherent; just use vm_insert_page() or > remap_page_range(). > Hello Clemens, On Mon, May 23, 2011 at 10:30 AM, Clemens Ladisch wrote: > Leon Woestenberg wrote: >> Having dma_mmap_coherent() there is good for one or two archs, but how >> can we built portable drivers if the others arch's are still missing? > > Easy: Resolve all issues, implement it for all the other arches, and add > it to the official DMA API. > I could send patches, but I would get bashed. Would be a learning experience though (and a long email thread). >> How would dma_mmap_coherent() look like on x86? > > X86 and some others are always coherent; just use vm_insert_page() or > remap_page_range(). > For x86 (my current test system) I tend to go with remap_page_range() so that the mapping is done before the pages are actually touched. With that I leave the work-in-progress (dma_mmap_coherent) aside for a moment, I'll revisit that later on ARM. However, I still feel I'm treading sandy waters, not familiar enough with the VM internals. Does memory allocated with pci_alloc_consistent() need a get_page() in the driver before I remap_page_range() it? Does memory allocated with __get_free_pages() need a get_page() in the driver before I remap_page_range() it? And how about set_bit(PG_reserved, ...) on those pages? Is that something of the past? #if 0 ... ... #else /* remap_pfn_range */ #warning Using remap_pfn_range static int buffer_mmap(struct file *file, struct vm_area_struct *vma) { unsigned long vsize, vsize2; void *vaddr, *vaddr2; unsigned long start = vma->vm_start; * VM_RESERVED: prevent the pages from being swapped out */ vma->vm_flags |= VM_RESERVED; vma->vm_private_data = file->private_data; /* allocated using __get_free_pages() or pci_alloc_consistent() */ vaddr = buffer_virt; vsize = buffer_size; /* iterate over pages */ vaddr2 = vaddr; vsize2 = vsize; while (vsize2 > 0) { printk(KERN_DEBUG "get_page(page=%p)\n", virt_to_page(vaddr2)); get_page(virt_to_page(vaddr2)); //set_bit(PG_reserved, &(virt_to_page(vaddr2)->flags)); vaddr2 += PAGE_SIZE; vsize2 -= PAGE_SIZE; } remap_pfn_range(vma, vma->vm_start, page_to_pfn(virt_to_page(vaddr)), vsize, vma->vm_page_prot); return 0; } #endif Thanks for the explanation, Regards, -- Leon -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org