Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755587Ab3GQPSV (ORCPT ); Wed, 17 Jul 2013 11:18:21 -0400 Received: from service87.mimecast.com ([91.220.42.44]:43183 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752025Ab3GQPSR convert rfc822-to-8bit (ORCPT ); Wed, 17 Jul 2013 11:18:17 -0400 Message-ID: <51E6B5B9.4090506@arm.com> Date: Wed, 17 Jul 2013 16:18:17 +0100 From: Sudeep KarkadaNagesha User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130623 Thunderbird/17.0.7 MIME-Version: 1.0 To: Rob Herring CC: Sudeep KarkadaNagesha , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "cpufreq@vger.kernel.org" , "linux-pm@vger.kernel.org" , "devicetree-discuss@lists.ozlabs.org" , Russell King , Shawn Guo , Gregory Clement , Greg Kroah-Hartman , Viresh Kumar , "Rafael J. Wysocki" , "grant.likely@linaro.org" , Lorenzo Pieralisi , Olof Johansson , Arnd Bergmann Subject: Re: [RFC PATCH v2 01/15] of: add support for retrieving cpu node for a given logical cpu index References: <1374069984-20567-1-git-send-email-Sudeep.KarkadaNagesha@arm.com> <1374069984-20567-2-git-send-email-Sudeep.KarkadaNagesha@arm.com> <51E6AF49.20403@gmail.com> In-Reply-To: <51E6AF49.20403@gmail.com> X-OriginalArrivalTime: 17 Jul 2013 15:18:13.0953 (UTC) FILETIME=[DB1AD310:01CE8300] X-MC-Unique: 113071716181409201 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4272 Lines: 108 On 17/07/13 15:50, Rob Herring wrote: > On 07/17/2013 09:06 AM, Sudeep.KarkadaNagesha@arm.com wrote: >> From: Sudeep KarkadaNagesha >> >> Currently different drivers requiring to access cpu device node are >> parsing the device tree themselves. Since the ordering in the DT need >> not match the logical cpu ordering, the parsing logic needs to consider >> that. However, this has resulted in lots of code duplication and in some >> cases even incorrect logic. >> >> It's better to consolidate them by adding support for getting cpu >> device node for a given logical cpu index in DT core library. However >> logical to physical index mapping can be architecture specific. >> >> This patch adds of_get_cpu_node to retrieve a cpu device node for a >> given logical cpu index. The default matching of the physical id to the >> logical cpu index can be overridden by architecture specific code. >> >> It is recommended to use these helper function only in pre-SMP/early >> initialisation stages to retrieve CPU device node pointers in logical >> ordering. Once the cpu devices are registered, it can be retrieved easily >> from cpu device of_node which avoids unnecessary parsing and matching. >> >> Cc: Rob Herring >> Signed-off-by: Sudeep KarkadaNagesha > > One comment below, but otherwise for patches 1-4, 8 and 9: > > Acked-by: Rob Herring > > Also, patch 3 needs to come before patch 2 or the matching will be wrong > if patch 3 is not applied. Ah, correct will fix it in next version. > >> --- >> drivers/of/base.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ >> include/linux/of.h | 5 +++++ >> 2 files changed, 71 insertions(+) >> >> diff --git a/drivers/of/base.c b/drivers/of/base.c >> index 5c54279..363b8f9 100644 >> --- a/drivers/of/base.c >> +++ b/drivers/of/base.c >> @@ -230,6 +230,72 @@ const void *of_get_property(const struct device_node *np, const char *name, >> } >> EXPORT_SYMBOL(of_get_property); >> >> +/* >> + * arch_match_cpu_phys_id - Match the given logical CPU and physical id >> + * >> + * @cpu: logical index of a cpu >> + * @phys_id: physical identifier of a cpu >> + * >> + * CPU logical to physical index mapping is architecure specific. >> + * However this __weak function provides a default match of physical >> + * id to logical cpu index. >> + * >> + * Returns 1 if the physical identifier and the logical index correspond >> + * to the same cpu, 0 otherwise. >> + */ >> +int __weak arch_match_cpu_phys_id(int cpu, u64 phys_id) >> +{ >> + return (u32)phys_id == cpu; >> +} >> + >> +/** >> + * of_get_cpu_node - Get device node associated with the given logical CPU >> + * >> + * @cpu: CPU number(logical index) for which device node is required >> + * >> + * The main purpose of this function is to retrieve the device node for the >> + * given logical CPU index. It should be used to intialise the of_node in >> + * cpu device. Once of_node in cpu device is populated, all the further >> + * references can use that instead. >> + * >> + * CPU logical to physical index mapping is architecure specific and is built >> + * before booting secondary cores. This function uses arch_match_cpu_phys_id >> + * which can be overridden by architecture specific implementation. >> + * >> + * Returns a node pointer for the logical cpu if found, else NULL. >> + */ >> +struct device_node *of_get_cpu_node(int cpu) >> +{ >> + struct device_node *cpun, *cpus; >> + const u32 *cell; >> + u64 hwid; >> + int ac, prop_len; >> + >> + cpus = of_find_node_by_path("/cpus"); >> + if (WARN(!cpus, "Missing cpus node, bailing out\n")) > > What happens on a system with no /cpus nodes? Seems like this is another > case of adding new warnings to existing working systems. > > I'd replace all the WARN's with a single pr_warn on any errors below. > For missing /cpus, I would just silently return. Ah, forgot recent discussions on this, will fix it. Regards, Sudeep -- 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/