From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752858Ab3BUJIZ (ORCPT ); Thu, 21 Feb 2013 04:08:25 -0500 Received: from us02smtp1.synopsys.com ([198.182.60.75]:59166 "EHLO vaxjo.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752608Ab3BUJIV (ORCPT ); Thu, 21 Feb 2013 04:08:21 -0500 Message-ID: <5125E3F2.7070402@synopsys.com> Date: Thu, 21 Feb 2013 14:38:02 +0530 From: Vineet Gupta User-Agent: Mozilla/5.0 (X11; Linux i686; rv:16.0) Gecko/20121011 Thunderbird/16.0.1 MIME-Version: 1.0 To: James Hogan CC: , Vineet Gupta , Grant Likely , Arnd Bergmann , Rob Herring Subject: Re: [PATCH 1/2] metag: copy devicetree to non-init memory References: <1361371929-28148-1-git-send-email-james.hogan@imgtec.com> <1361371929-28148-2-git-send-email-james.hogan@imgtec.com> In-Reply-To: <1361371929-28148-2-git-send-email-james.hogan@imgtec.com> X-Enigmail-Version: 1.4.6 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.12.197.217] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi James, On Wednesday 20 February 2013 08:22 PM, James Hogan wrote: > Make a copy of the device tree blob in non-init memory. It is required > when using built-in device tree files that the platform code copies the > blob to non-init memory prior to calling unflatten_device_tree(), > otherwise the strings that the device tree refer to will get poisoned > and potentially reused, breaking later reading of the device tree > post-init (such as compatible matching in modules, debugfs, and the > procfs interface). While the patch conceptually looks correct, I'm not sure why any user of DT - post-init would refer to DT bindings using of_fdt_* API which use the flat tree, instead of the binary tree (more efficient in space/usage). Is this to support some in-transition drivers and other code. And if this is a general problem, then it is probably better done in DT core. I'm sure I'm missing something here. > Signed-off-by: James Hogan > --- > arch/metag/include/asm/prom.h | 1 + > arch/metag/kernel/devtree.c | 17 +++++++++++++++++ > arch/metag/kernel/setup.c | 2 ++ > 3 files changed, 20 insertions(+) > > diff --git a/arch/metag/include/asm/prom.h b/arch/metag/include/asm/prom.h > index d881396..ccac97e 100644 > --- a/arch/metag/include/asm/prom.h > +++ b/arch/metag/include/asm/prom.h > @@ -18,6 +18,7 @@ > #define HAVE_ARCH_DEVTREE_FIXUPS > > extern struct machine_desc *setup_machine_fdt(void *dt); > +extern void copy_fdt(void); > extern void metag_dt_memblock_reserve(void); > > #endif /* __ASM_METAG_PROM_H */ > diff --git a/arch/metag/kernel/devtree.c b/arch/metag/kernel/devtree.c > index 5b6b1d85..7cd0252 100644 > --- a/arch/metag/kernel/devtree.c > +++ b/arch/metag/kernel/devtree.c > @@ -95,3 +95,20 @@ struct machine_desc * __init setup_machine_fdt(void *dt) > > return mdesc_best; > } > + > +/** > + * copy_fdt - Copy device tree into non-init memory. > + * > + * We must copy the flattened device tree blob into non-init memory because the > + * unflattened device tree will reference the strings in it directly. > + */ > +void __init copy_fdt(void) > +{ > + void *alloc = early_init_dt_alloc_memory_arch( > + be32_to_cpu(initial_boot_params->totalsize), 0x40); > + if (alloc) { > + memcpy(alloc, initial_boot_params, > + be32_to_cpu(initial_boot_params->totalsize)); > + initial_boot_params = alloc; > + } > +} > diff --git a/arch/metag/kernel/setup.c b/arch/metag/kernel/setup.c > index dd6c5ad..8792461 100644 > --- a/arch/metag/kernel/setup.c > +++ b/arch/metag/kernel/setup.c > @@ -406,6 +406,8 @@ void __init setup_arch(char **cmdline_p) > cpu_2_hwthread_id[smp_processor_id()] = hard_processor_id(); > hwthread_id_2_cpu[hard_processor_id()] = smp_processor_id(); > > + /* Copy device tree blob into non-init memory before unflattening */ > + copy_fdt(); > unflatten_device_tree(); > > #ifdef CONFIG_SMP