From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934154AbaHZIKE (ORCPT ); Tue, 26 Aug 2014 04:10:04 -0400 Received: from mout.kundenserver.de ([212.227.17.24]:49311 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933905AbaHZIJ5 (ORCPT ); Tue, 26 Aug 2014 04:09:57 -0400 From: Arnd Bergmann To: Thierry Reding Cc: Stephen Warren , Andrew Bresticker , linux-tegra@vger.kernel.org, Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Russell King , Jassi Brar , Linus Walleij , Greg Kroah-Hartman , Mathias Nyman , Grant Likely , Alan Stern , Kishon Vijay Abraham I , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-usb@vger.kernel.org, Jonas Bonn , David Howells , Koichi Yasutake Subject: Re: [PATCH v2 2/9] mailbox: Add NVIDIA Tegra XUSB mailbox driver Date: Tue, 26 Aug 2014 10:09:25 +0200 Message-ID: <6589717.GOLq1GlTCJ@wuerfel> User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20140826075023.GB17263@ulmo> References: <1408381705-3623-1-git-send-email-abrestic@chromium.org> <3804028.YQzQ4uAVsf@wuerfel> <20140826075023.GB17263@ulmo> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V02:K0:PGrC/4H9GEsTLqaQ1Vmy3vBwYYBXTPfbHW3REFSdemS cYNtAIzbcaNWVQfsJXKfCcuUMXU4Q7gacIl3aDotARvJAcGLJQ q9kW74h1nklOM/Coyb0W3gkCQidtFhJfMHeeP+JWkTXnLYmPgB MV/g5vTdKZ/HumTvoVJolNx/F3cMbLfZY8ugxdt35bA+OSeoDZ Nw+YRsC0AV93x5cgrxgQoSwlefqzHWsQHE+uZuwtV/Loa2Yr0O RimpP9O4FHMGfA4S4LzJntzGDrUZudLCuWo8vELKMVsIOKguld bxZTzW7yY8aWqoVMEKk6iNpJWiB7e7EdS0JGB5GuZBfb2PpP78 Z2fNdaufu+36t1UgHU6Q= X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 26 August 2014 09:50:25 Thierry Reding wrote: > On Tue, Aug 26, 2014 at 09:43:50AM +0200, Arnd Bergmann wrote: > > On Tuesday 26 August 2014 08:57:31 Thierry Reding wrote: > > > On Mon, Aug 25, 2014 at 01:01:52PM -0600, Stephen Warren wrote: > > > > On 08/18/2014 11:08 AM, Andrew Bresticker wrote: > > > [...] > > > > >+static int tegra_xusb_mbox_probe(struct platform_device *pdev) > > > > > > > > >+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0); > > > > >+ if (!res) > > > > >+ return -ENODEV; > > > > > > > > Should devm_request_mem_region() be called here to claim the region? > > > > > > > > >+ mbox->regs = devm_ioremap_nocache(&pdev->dev, res->start, > > > > >+ resource_size(res)); > > > > >+ if (!mbox->regs) > > > > >+ return -ENOMEM; > > > > > > > > Is _nocache required? I don't see other drivers using it. I assume there's > > > > nothing special about the mbox registers. > > > > > > Most drivers should be using devm_ioremap_resource() which will use the > > > _nocache variant of devm_ioremap() when appropriate. Usually the region > > > will not be marked cacheable (IORESOURCE_CACHEABLE) and therefore be > > > remapped uncached. > > > > > > > Note that ioremap() and ioremap_nocache() are the same. We really shouldn't > > ever call ioremap_nocache(). > > Perhaps we should remove ioremap_nocache() in that case. Or ioremap(), > really, and keep only those variants that do what they claim to do. That would be good, but there are many instances of either one: arnd@wuerfel:/git/arm-soc$ git grep -w ioremap | wc 2156 13402 183732 arnd@wuerfel:/git/arm-soc$ git grep -w ioremap_nocache | wc 485 2529 42955 FWIW, I just looked through all architectures and found three on which ioremap and ioremap_nocache are not the same, and ioremap defaults to cacheable: - OpenRISC so far only supports running in a simulator, so this is likely to be a bug that will get hit on actual hardware with MMIO. Jonas should probably look into this. - mn10300 has no MMU and doesn't really use ioremap, but it should still be fixed for PCI drivers using it on the one board that supports PCI. - cris seems to have been broken forever. > > devm_ioremap_resource() and pci_iomap() checking for IORESOURCE_CACHEABLE is > > rather silly, since it doesn't call ioremap_cache() in that case. > > Then that should be fixed. Yes. I'd suggest we just ignore that flag and always call ioremap here. When I checked this before, IORESOURCE_CACHEABLE only ever gets set for PCI ROM BARs, which we don't map into the kernel. Arnd