Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755926Ab3GQOu4 (ORCPT ); Wed, 17 Jul 2013 10:50:56 -0400 Received: from mail-ie0-f171.google.com ([209.85.223.171]:48724 "EHLO mail-ie0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755800Ab3GQOuy (ORCPT ); Wed, 17 Jul 2013 10:50:54 -0400 Message-ID: <51E6AF49.20403@gmail.com> Date: Wed, 17 Jul 2013 09:50:49 -0500 From: Rob Herring User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: Sudeep.KarkadaNagesha@arm.com CC: 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 , 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> In-Reply-To: <1374069984-20567-2-git-send-email-Sudeep.KarkadaNagesha@arm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4581 Lines: 125 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. > --- > 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. Rob > + return NULL; > + > + if (WARN_ON(of_property_read_u32(cpus, "#address-cells", &ac))) > + ac = of_n_addr_cells(cpus); > + > + for_each_child_of_node(cpus, cpun) { > + if (of_node_cmp(cpun->type, "cpu")) > + continue; > + cell = of_get_property(cpun, "reg", &prop_len); > + if (WARN(!cell, "%s: missing reg property\n", cpun->full_name)) > + continue; > + > + while (prop_len) { > + hwid = of_read_number(cell, ac); > + prop_len -= ac; > + if (arch_match_cpu_phys_id(cpu, hwid)) > + return cpun; > + } > + } > + > + return NULL; > +} -- 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/