On 03/26/2013 10:51 AM, Viresh Kumar wrote: > big LITTLE is ARM's new Architecture focussing power/performance needs of modern > world. More information about big LITTLE can be found here: > > http://www.arm.com/products/processors/technologies/biglittleprocessing.php > http://lwn.net/Articles/481055/ > > In order to keep cpufreq support for all big LITTLE platforms simple/generic, > this patch tries to add a generic cpufreq driver layer for all big LITTLE > platforms. > > The driver is divided into two parts: > - Core driver: Generic and shared across all big LITTLE SoC's > - Glue drivers: Per platform drivers providing ops to the core driver > > This patch adds in a generic glue driver which would extract information from > Device Tree. > > Future SoC's can either reuse the DT glue or write their own depending on the > need. > > Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@xxxxxxx> > Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx> [...] > diff --git a/drivers/cpufreq/arm_big_little_dt.c b/drivers/cpufreq/arm_big_little_dt.c > new file mode 100644 > index 0000000..452ff46 > --- /dev/null > +++ b/drivers/cpufreq/arm_big_little_dt.c > @@ -0,0 +1,92 @@ > +/* > + * Generic big.LITTLE CPUFreq Interface driver > + * > + * It provides necessary ops to arm_big_little cpufreq driver and gets > + * Frequency information from Device Tree. Freq table in DT must be in KHz. > + * > + * Copyright (C) 2013 Linaro. > + * Viresh Kumar <viresh.kumar@xxxxxxxxxx> > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License version 2 as > + * published by the Free Software Foundation. > + * > + * This program is distributed "as is" WITHOUT ANY WARRANTY of any > + * kind, whether express or implied; without even the implied warranty > + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + */ > + > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > + > +#include <linux/cpufreq.h> > +#include <linux/device.h> > +#include <linux/export.h> > +#include <linux/module.h> > +#include <linux/of.h> > +#include <linux/opp.h> > +#include <linux/slab.h> > +#include <linux/types.h> > +#include "arm_big_little.h" > + > +static int dt_init_opp_table(struct device *cpu_dev) > +{ > + struct device_node *np = NULL; > + int count = 0, ret; > + > + for_each_child_of_node(of_find_node_by_path("/cpus"), np) { If of_find_node_by_path() returns NULL, there will be a NULL pointer dereference. > + if (count++ != cpu_dev->id) > + continue; > + if (!of_get_property(np, "operating-points", NULL)) > + return -ENODATA; > + > + cpu_dev->of_node = np; > + > + ret = of_init_opp_table(cpu_dev); > + if (ret) > + return ret; > + > + return 0; of_node_put() should be called on np before returning. Also, the reference count of the parent node should be decremented as well. These comments apply to the below function dt_get_transition_latency() too. > + } > + > + return -ENODEV; > +} > + > +static int dt_get_transition_latency(struct device *cpu_dev) > +{ > + struct device_node *np = NULL; > + u32 transition_latency = CPUFREQ_ETERNAL; > + int count = 0; > + > + for_each_child_of_node(of_find_node_by_path("/cpus"), np) { > + if (count++ != cpu_dev->id) > + continue; > + > + of_property_read_u32(np, "clock-latency", &transition_latency); > + return 0; > + } > + > + return -ENODEV; > +} -- Francesco -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
