Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753942AbbG0Jkl (ORCPT ); Mon, 27 Jul 2015 05:40:41 -0400 Received: from mga14.intel.com ([192.55.52.115]:28835 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753762AbbG0Jkk (ORCPT ); Mon, 27 Jul 2015 05:40:40 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.15,552,1432623600"; d="scan'208";a="736123449" Message-ID: <1437989891.22168.15.camel@intel.com> Subject: Re: [PATCH V7 4/5] arm64: apei: implement arch_apei_get_mem_attributes() From: Matt Fleming To: Will Deacon CC: Catalin Marinas , "Jonathan (Zhixiong) Zhang" , "fu.wei@linaro.org" , "al.stone@linaro.org" , "rjw@rjwysocki.net" , "linux-kernel@vger.kernel.org" , "linaro-acpi@lists.linaro.org" Date: Mon, 27 Jul 2015 10:38:11 +0100 In-Reply-To: <20150724162600.GA21177@arm.com> References: <1437515960-16812-1-git-send-email-zjzhang@codeaurora.org> <1437515960-16812-5-git-send-email-zjzhang@codeaurora.org> <20150724145707.GD12569@arm.com> <20150724162149.GX3550@e104818-lin.cambridge.arm.com> <20150724162600.GA21177@arm.com> Organization: Intel Corporation (UK) Ltd. - Registered No. 1134945 - Pipers Way, Swindon SN3 1RJ Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11 (3.12.11-1.fc21) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Originating-IP: [163.33.239.180] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1932 Lines: 45 On Fri, 2015-07-24 at 17:26 +0100, Will Deacon wrote: > On Fri, Jul 24, 2015 at 05:21:49PM +0100, Catalin Marinas wrote: > > On Fri, Jul 24, 2015 at 03:57:08PM +0100, Will Deacon wrote: > > > On Tue, Jul 21, 2015 at 10:59:19PM +0100, Jonathan (Zhixiong) Zhang wrote: > > > > diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h > > > > +static inline pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr) > > > > +{ > > > > + pgprot_t prot; > > > > + > > > > + prot = efi_mem_attributes(addr); > > > > + if (prot & EFI_MEMORY_UC) > > > > + return PROT_DEVICE_nGnRnE; > > > > + if (prot & EFI_MEMORY_WC) > > > > + return PROT_NORMAL_NC; > > > > > > Can we not use pgprot_noncached and pgprot_writecombine for these two? > > > > Actually, why do we even use pgprot_t for prot here? EFI_MEMORY_* don't > > have anything to do with the arch-specific pgprot_t. > > Good point; the pgprot_t confused me, so my suggestion is much use after > ll. We're better off with a u64 to avoid further confusion. Isn't the whole point of arch_apei_get_mem_attribute() to turn an arch-independent memory attribute (EFI_MEMORY_*) into an arch-specific value to pass to ioremap_page_range()? I don't see how you can do that any other way than by using pgprot_t. Really, the problem here is that ioremap_page_caller() has no notion of "map this range in a firmware-compatible manner". If we could do, for example, ioremap_page_range(vaddr, vend, paddr, PAGE_FW_COMPAT); that would allow the innards of the arch-ioremap to figure out exactly how to map this range so that the firmware could access it coherently. I suggested this previously but it didn't gain any traction. -- 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/