Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751714AbaDSLdX (ORCPT ); Sat, 19 Apr 2014 07:33:23 -0400 Received: from moutng.kundenserver.de ([212.227.17.24]:62654 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751081AbaDSLdT (ORCPT ); Sat, 19 Apr 2014 07:33:19 -0400 From: Arnd Bergmann To: Rob Herring Subject: Re: [PATCH 4/8] tty/serial: add generic serial earlycon Date: Sat, 19 Apr 2014 13:32:24 +0200 User-Agent: KMail/1.12.2 (Linux/3.8.0-22-generic; KDE/4.3.2; x86_64; ; ) Cc: Alan Cox , "linux-arm-kernel@lists.infradead.org" , Catalin Marinas , Russell King , "Greg Kroah-Hartman" , "x86@kernel.org" , Will Deacon , "linux-kernel@vger.kernel.org" , "linux-serial@vger.kernel.org" , Jiri Slaby References: <1395436128-11244-1-git-send-email-robherring2@gmail.com> <21117957.8m9iUdR1VN@wuerfel> In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201404191332.24392.arnd@arndb.de> X-Provags-ID: V02:K0:aaAi2lVSv1JxDGs8gRyhJeqohqn9xyWDkvaY1vxn3lQ sssAfq2cF3ayVpTCFS0i+gkIQwwrE25PT/PzA5PUI6K+QpUj4Z YsyC7XoVCx7MzQZZowOujkzZIhEWVQILVirCPSI01GaR0z+zum c2ogzOJ3IV3a1TbM4YpKWkMulkGgYlwfxloyT3Ou31FKoeK33e Rh1TUn4gAUKqC1XIbCFyegEWlGkTQB0uJd84RAIdArUDwLdu9M a0n/MMi/V3HgqAXk3uM2ZaRfl5QXDn+7x/9CUIpen4abF/6O5y N/KlMCShc7PINn3/gsPpWivAz/2khdPuP2p8Y/YwLJTeXqATkM 7fsPUJWJpavr6C9R7N2Gj1Sd5jJNBhxa9LxTqPFP9 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 17 April 2014, Rob Herring wrote: > On Mon, Mar 24, 2014 at 10:42 AM, Arnd Bergmann wrote: > > On Monday 24 March 2014 08:36:46 Rob Herring wrote: > >> On Mon, Mar 24, 2014 at 6:29 AM, Arnd Bergmann wrote: > >> > On Monday 24 March 2014 11:22:03 Catalin Marinas wrote: > >> >> On Fri, Mar 21, 2014 at 09:08:44PM +0000, Rob Herring wrote: > >> >> > diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c > >> >> > new file mode 100644 > >> >> > index 0000000..241757a > >> >> > --- /dev/null > >> >> > +++ b/drivers/tty/serial/earlycon.c > >> >> [...] > >> >> > +static void __iomem * __init earlycon_map(unsigned long paddr, size_t size) > >> >> > +{ > >> >> > + void __iomem *base; > >> >> > +#ifdef CONFIG_FIX_EARLYCON_MEM > >> >> > + set_fixmap_nocache(FIX_EARLYCON_MEM_BASE, paddr & PAGE_MASK); > >> >> > + base = (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE); > >> >> > + base += paddr & ~PAGE_MASK; > >> >> > +#else > >> >> > + base = ioremap_nocache(paddr, size); > >> >> > +#endif > >> >> > >> >> Just curious why not set_fixmap_io (and plain ioremap)? > >> > > >> > Good point. Note that ioremap_nocache() is the same as ioremap() > >> > on *all* architectures. > > Did you mean "not the same"? No > Why are there 2 flavors if they are > always the same. I assume it's just a mistake someone made a long time ago and nobody ever changed it because they didn't want to break obscure code. x86 seems to be a bit odd here, because is has both page-table and MTRR method of setting up whether an access can be cached or not. This may have led to the introduction of the _nocache variant, when the regular ioremap was already uncached on all other architectures but cached on x86. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/