From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 21 Jan 2001 03:37:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 21 Jan 2001 03:37:04 -0500 Received: from colorfullife.com ([216.156.138.34]:5902 "EHLO colorfullife.com") by vger.kernel.org with ESMTP id ; Sun, 21 Jan 2001 03:36:50 -0500 Message-ID: <3A6A9F9A.3CDE1B05@colorfullife.com> Date: Sun, 21 Jan 2001 09:36:42 +0100 From: Manfred Spraul X-Mailer: Mozilla 4.75 [en] (X11; U; Linux 2.2.16-22 i586) X-Accept-Language: en MIME-Version: 1.0 To: Russell King CC: Johannes Erdfelt , linux-kernel@vger.kernel.org Subject: Re: Inefficient PCI DMA usage (was: [experimental patch] UHCI updates) In-Reply-To: <200101202315.f0KNFTV01790@flint.arm.linux.org.uk> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Russell King wrote: > > Johannes Erdfelt writes: > > They need to be visible via DMA. They need to be 16 byte aligned. We > > also have QH's which have similar requirements, but we don't use as many > > of them. > > Can we get away from the "16 byte aligned" and make it "n byte aligned"? > I believe that slab already has support for this? > Not yet, but that would be a 2 line patch (currently it's hardcoded to BYTES_PER_WORD align or L1_CACHE_BYTES, depending on the HWCACHE_ALIGN flag). But there are 2 other problems: * kmem_cache_alloc returns one pointer, pci_alloc_consistent 2 pointers: one dma address, one virtual address. * The code relies on the virt_to_page() macro. The second problem is the difficult one, I don't see how I could remove that dependency without a major overhaul. -- Manfred - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/