From mboxrd@z Thu Jan 1 00:00:00 1970 From: robherring2@gmail.com (Rob Herring) Date: Tue, 16 Oct 2012 15:42:43 -0500 Subject: [RFC PATCH 1/4] ARM: kernel: add device tree init map function In-Reply-To: <1350393709-23546-2-git-send-email-lorenzo.pieralisi@arm.com> References: <1350393709-23546-1-git-send-email-lorenzo.pieralisi@arm.com> <1350393709-23546-2-git-send-email-lorenzo.pieralisi@arm.com> Message-ID: <507DC6C3.6090403@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 10/16/2012 08:21 AM, Lorenzo Pieralisi wrote: > When booting through a device tree, the kernel cpu logical id map can be > initialized using device tree data passed by FW or through an embedded blob. > > This patch adds a function that parses device tree "cpu" nodes and > retrieves the corresponding CPUs hardware identifiers (MPIDR). > It sets the possible cpus and the cpu logical map values according to > the number of CPUs defined in the device tree and respective properties. > > The primary CPU is assigned cpu logical number 0 to keep the current > convention valid. > > Current bindings documentation is included in the patch: > > Documentation/devicetree/bindings/arm/cpus.txt > > Signed-off-by: Lorenzo Pieralisi > --- > Documentation/devicetree/bindings/arm/cpus.txt | 42 +++++++++++++++++++++++ > arch/arm/include/asm/prom.h | 2 ++ > arch/arm/kernel/devtree.c | 47 ++++++++++++++++++++++++++ > 3 files changed, 91 insertions(+) > create mode 100644 Documentation/devicetree/bindings/arm/cpus.txt > > diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt > new file mode 100644 > index 0000000..897f3b4 > --- /dev/null > +++ b/Documentation/devicetree/bindings/arm/cpus.txt > @@ -0,0 +1,42 @@ > +* ARM CPUs binding description > + > +The device tree allows to describe the layout of CPUs in a system through > +the "cpus" node, which in turn contains a number of subnodes (ie "cpu") > +defining properties for every cpu. > + > +Bindings for CPU nodes follow the ePAPR standard, available from: > + > +http://devicetree.org > + > +For the ARM architecture every CPU node must contain the following property: > + > +- reg : property defining the CPU MPIDR[23:0] register bits defining or matching the MPIDR? > + > +Every cpu node is required to set its device_type to "cpu". This is a bit questionable as device_type is deprecated for FDT. However, since the ePAPR defines using it You should add a compatible property for the cpu model. > + > +Example: > + > + cpus { > + #size-cells = <0>; > + #address-cells = <1>; > + > + CPU0: cpu at 0 { > + device_type = "cpu"; > + reg = <0x0>; > + }; > + > + CPU1: cpu at 1 { > + device_type = "cpu"; > + reg = <0x1>; > + }; > + > + CPU2: cpu at 100 { > + device_type = "cpu"; > + reg = <0x100>; > + }; > + > + CPU3: cpu at 101 { > + device_type = "cpu"; > + reg = <0x101>; > + }; > + }; > diff --git a/arch/arm/include/asm/prom.h b/arch/arm/include/asm/prom.h > index aeae9c6..8dd51dc 100644 > --- a/arch/arm/include/asm/prom.h > +++ b/arch/arm/include/asm/prom.h > @@ -15,6 +15,7 @@ > > extern struct machine_desc *setup_machine_fdt(unsigned int dt_phys); > extern void arm_dt_memblock_reserve(void); > +extern void __init arm_dt_init_cpu_maps(void); > > #else /* CONFIG_OF */ > > @@ -24,6 +25,7 @@ static inline struct machine_desc *setup_machine_fdt(unsigned int dt_phys) > } > > static inline void arm_dt_memblock_reserve(void) { } > +static inline void arm_dt_init_cpu_maps(void) { } > > #endif /* CONFIG_OF */ > #endif /* ASMARM_PROM_H */ > diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c > index bee7f9d..c86e414 100644 > --- a/arch/arm/kernel/devtree.c > +++ b/arch/arm/kernel/devtree.c > @@ -19,8 +19,10 @@ > #include > #include > > +#include > #include > #include > +#include > #include > #include > > @@ -61,6 +63,51 @@ void __init arm_dt_memblock_reserve(void) > } > } > > +/* > + * arm_dt_init_cpu_maps - Function retrieves cpu nodes from the device tree > + * and builds the cpu logical map array containing MPIDR values related to > + * logical cpus > + * > + * Updates the cpu possible mask with the number of parsed cpu nodes > + */ > +void __init arm_dt_init_cpu_maps(void) > +{ > + struct device_node *dn = NULL; > + int i, cpu = 1; > + > + while ((dn = of_find_node_by_type(dn, "cpu")) && cpu <= nr_cpu_ids) { I think all /cpu nodes would have the right type. You could use for_each_child_of_node here. > + const u32 *hwid; > + int len; > + > + pr_debug(" * %s...\n", dn->full_name); > + > + hwid = of_get_property(dn, "reg", &len); > + Use of_property_read_u32. > + if (!hwid || len != 4) { > + pr_err(" * %s missing reg property\n", dn->full_name); > + continue; > + } > + /* > + * We want to assign the boot CPU logical id 0. > + * Boot CPU checks its own MPIDR and if matches the current > + * cpu node "reg" value it sets the logical cpu index to 0 > + * and stores the physical id accordingly. > + * If MPIDR does not match, assign sequential cpu logical > + * id (starting from 1) and increments it. > + */ > + i = (be32_to_cpup(hwid) == (read_cpuid_mpidr() & 0xffffff)) > + ? 0 : cpu++; > + > + if (!i) > + printk(KERN_INFO "Booting Linux on CPU HWID 0x%x\n", > + be32_to_cpup(hwid)); > + > + cpu_logical_map(i) = be32_to_cpup(hwid); > + > + set_cpu_possible(i, true); > + } > +} > + > /** > * setup_machine_fdt - Machine setup when an dtb was passed to the kernel > * @dt_phys: physical address of dt blob >