From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 22 Jan 2001 01:31:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 22 Jan 2001 01:31:46 -0500 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:12555 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id ; Mon, 22 Jan 2001 01:31:37 -0500 From: Russell King Message-Id: <200101212311.f0LNBvm01377@flint.arm.linux.org.uk> Subject: Re: Inefficient PCI DMA usage (was: [experimental patch] UHCI updates) To: johannes@erdfelt.com (Johannes Erdfelt) Date: Sun, 21 Jan 2001 23:11:56 +0000 (GMT) Cc: manfred@colorfullife.com (Manfred Spraul), linux-kernel@vger.kernel.org In-Reply-To: <20010121123730.N9156@sventech.com> from "Johannes Erdfelt" at Jan 21, 2001 12:37:31 PM X-Location: london.england.earth.mulky-way.universe X-Mailer: ELM [version 2.5 PL3] MIME-Version: 1.0 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 Hi, You may have already found out that there's a problem using pci_alloc_consistent and friends in the USB layer which will only be obvious on CPUs where they need to do page table remapping - that is that pci_alloc_consistent/pci_free_consistent aren't guaranteed to be interrupt-safe. I'm not sure what the correct way around this is yet, but I do know its a major problem. ;( Maybe we need to do a get_free_pages-type thing with this and keep a set amount of consistent area in reserve for atomic allocations (as per GFP_ATOMIC)? Yes, I know its not nice, but I don't see any other option at the moment with USB. (yes, I'm hacking the 2.2.18 ohci driver for my own ends to get something up and running on one of my machines). _____ |_____| ------------------------------------------------- ---+---+- | | Russell King rmk@arm.linux.org.uk --- --- | | | | http://www.arm.linux.org.uk/personal/aboutme.html / / | | +-+-+ --- -+- / | THE developer of ARM Linux |+| /|\ / | | | --- | +-+-+ ------------------------------------------------- /\\\ | - 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/