From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann 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> References: <1408381705-3623-1-git-send-email-abrestic@chromium.org> <3804028.YQzQ4uAVsf@wuerfel> <20140826075023.GB17263@ulmo> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <20140826075023.GB17263@ulmo> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Thierry Reding Cc: Stephen Warren , Andrew Bresticker , linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.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-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jonas Bonn , David Howells , Koichi Yasutake List-Id: devicetree@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 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html