Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757714AbaAFXms (ORCPT ); Mon, 6 Jan 2014 18:42:48 -0500 Received: from comal.ext.ti.com ([198.47.26.152]:39935 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757294AbaAFXmp (ORCPT ); Mon, 6 Jan 2014 18:42:45 -0500 Message-ID: <52CB3F55.1050404@ti.com> Date: Mon, 6 Jan 2014 18:42:13 -0500 From: Santosh Shilimkar User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Russell King - ARM Linux CC: =?UTF-8?B?S3J6eXN6dG9mIEhhxYJhc2E=?= , Linus Torvalds , lkml , Subject: Re: Regression (ARM) arch/arm/mm/init.c doesn't build without CONFIG_ARM_PATCH_PHYS_VIRT. References: <20140106223906.GH27432@n2100.arm.linux.org.uk> In-Reply-To: <20140106223906.GH27432@n2100.arm.linux.org.uk> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday 06 January 2014 05:39 PM, Russell King - ARM Linux wrote: > On Mon, Jan 06, 2014 at 08:28:20PM +0100, Krzysztof Hałasa wrote: >> Russell, Santosh, >> >> the unneeded commit causing regression is still in place. Please try to >> compile an ARM kernel without CONFIG_ARM_PATCH_PHYS_VIRT and with >> CONFIG_ZONE_DMA and see for yourself, if you don't believe me. >> >> Please be aware that this commit fixes nothing, its only function is >> causing the regression - so we don't lose anything by reverting it. >> >> If the attached wasn't clear, what the defective commit presently does >> is changing a perfectly valid code into a code referencing a variable >> which (without CONFIG_ARM_PATCH_PHYS_VIRT set) doesn't at all exist. >> >> With CONFIG_ARM_PATCH_PHYS_VIRT set, this commit does precisely nothing. > > Right, so, with Assabet, which has CONFIG_DMA_ZONE=y and > CONFIG_ARM_PATCH_PHYS_VIRT=y: > > $ make O=../build/assabet arch/arm/mm/init.i > > gives: > arm_dma_limit = __pv_phys_offset + arm_dma_zone_size - 1; > > with or without Santosh's patch. So, with V2P patching in place, there's > absolutely no functional difference. > > With CONFIG_ARM_PATCH_PHYS_VIRT=n, before Santosh's patch: > > arm_dma_limit = (0xc0000000UL) + arm_dma_zone_size - 1; > > After: > > arm_dma_limit = __pv_phys_offset + arm_dma_zone_size - 1; > > and this breaks the build because there is no __pv_phys_offset symbol. > > Now, the case which matters for Santosh is the first case - the one > where CONFIG_ARM_PATCH_PHYS_VIRT=y. We can clearly see that after > preprocessing, the results are 100% identical. > > Therefore, I find myself agreeing with Krzysztof that the commit is > bad, has no functional change for the case it was proposed to solve, > and needs to be reverted. > May be I missed your point but I ended up creating the patch because the CMA reservation was failing on Keystone since the arm_dma_limit wasn't right since it wasn't considering the actual __pv_phys_offset. Isn't that an issue ? Regards, Santosh -- 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/