On 03/26/2013 04:51 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@arm.com Signed-off-by: Viresh Kumar viresh.kumar@linaro.org
V1->V2:
- It was reviewed here earlier: https://lkml.org/lkml/2013/3/4/614
- It supports OPP library now and doesn't create a new binding for cpufreq table
- It doesn't add any dependency on cluster node in DT, rather we work with existing cpu nodes, Documentation updated.
- cpu_dev used because of OPP library and hence dev_err/dbg/info used at multiple places.
- Interface with glue driver updated a bit
- IS_ERR_OR_NULL replaced with IS_ERR for clk_get
- clk_get_sys used instead of clk_get and name of clk is also updated
- Few more minor cleanups done.
It is pushed here:
http://git.linaro.org/gitweb?p=people/vireshk/linux.git%3Ba=shortlog%3Bh=ref...
.../bindings/cpufreq/arm_big_little_dt.txt | 65 +++++ MAINTAINERS | 11 + drivers/cpufreq/Kconfig.arm | 12 + drivers/cpufreq/Makefile | 4 + drivers/cpufreq/arm_big_little.c | 282 +++++++++++++++++++++ drivers/cpufreq/arm_big_little.h | 40 +++ drivers/cpufreq/arm_big_little_dt.c | 92 +++++++ 7 files changed, 506 insertions(+) create mode 100644 Documentation/devicetree/bindings/cpufreq/arm_big_little_dt.txt create mode 100644 drivers/cpufreq/arm_big_little.c create mode 100644 drivers/cpufreq/arm_big_little.h create mode 100644 drivers/cpufreq/arm_big_little_dt.c
diff --git a/Documentation/devicetree/bindings/cpufreq/arm_big_little_dt.txt b/Documentation/devicetree/bindings/cpufreq/arm_big_little_dt.txt new file mode 100644 index 0000000..34a460d --- /dev/null +++ b/Documentation/devicetree/bindings/cpufreq/arm_big_little_dt.txt @@ -0,0 +1,65 @@ +Generic ARM big LITTLE cpufreq driver's DT glue +-----------------------------------------------
+This is DT specific glue layer for generic cpufreq driver for big LITTLE +systems.
I fail to see anything bL specific here. This is just multi-cluster, but even for that I don't see anything new other than simply allowing per cpu or per cluster opp's. The fact that we have one opp for a cluster is simply an implementation decision in CortexA cores.
+Both required and optional properties listed below must be defined +under node /cpus/cpu@x. Where x is the first cpu inside a cluster.
+NOTE: Cpus should boot in the order specified in DT and all cpus for a cluster +must be present contiguously. Generic DT driver will check only node 'x' for +cpu:x.
The OS cannot necessarily control the order. The OS should be able to boot on which ever core comes up first.
+Required properties: +- operating-points: Refer to Documentation/devicetree/bindings/power/opp.txt
- for details
+Optional properties: +- clock-latency: Specify the possible maximum transition latency for clock,
- in unit of nanoseconds.
Don't we already have "transition-latency" defined? Don't create something new. Ideally, this should have had "-ns" appended, but the binding is already defined.
+Examples:
+cpus {
- #address-cells = <1>;
- #size-cells = <0>;
- cpu@0 {
compatible = "arm,cortex-a15";reg = <0>;next-level-cache = <&L2>;operating-points = </* kHz uV */792000 1100000396000 950000198000 850000>;clock-latency = <61036>; /* two CLK32 periods */- };
- cpu@1 {
compatible = "arm,cortex-a15";reg = <1>;next-level-cache = <&L2>;- };
- cpu@100 {
compatible = "arm,cortex-a7";reg = <100>;next-level-cache = <&L2>;operating-points = </* kHz uV */792000 950000396000 750000198000 450000>;clock-latency = <61036>; /* two CLK32 periods */- };
- cpu@101 {
compatible = "arm,cortex-a7";reg = <101>;next-level-cache = <&L2>;- };
+}; diff --git a/MAINTAINERS b/MAINTAINERS index 4cf5fd3..4071b71 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2206,6 +2206,17 @@ S: Maintained F: drivers/cpufreq/ F: include/linux/cpufreq.h +CPU FREQUENCY DRIVERS - ARM BIG LITTLE +M: Viresh Kumar viresh.kumar@linaro.org +M: Sudeep KarkadaNagesha sudeep.karkadanagesha@arm.com +L: cpufreq@vger.kernel.org +L: linux-pm@vger.kernel.org +W: http://www.arm.com/products/processors/technologies/biglittleprocessing.php +S: Maintained +F: drivers/cpufreq/arm_big_little.h +F: drivers/cpufreq/arm_big_little.c +F: drivers/cpufreq/arm_big_little_dt.c
CPUID/MSR DRIVER M: "H. Peter Anvin" hpa@zytor.com S: Maintained diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm index 030ddf6..87b7e48 100644 --- a/drivers/cpufreq/Kconfig.arm +++ b/drivers/cpufreq/Kconfig.arm @@ -2,6 +2,18 @@ # ARM CPU Frequency scaling drivers # +config ARM_BIG_LITTLE_CPUFREQ
- tristate
- depends on ARM_CPU_TOPOLOGY
+config ARM_DT_BL_CPUFREQ
- tristate "Generic ARM big LITTLE CPUfreq driver probed via DT"
- select ARM_BIG_LITTLE_CPUFREQ
- depends on OF && HAVE_CLK
- help
This enables the Generic CPUfreq driver for ARM big.LITTLE platform.This gets frequency tables from DT.config ARM_OMAP2PLUS_CPUFREQ bool "TI OMAP2+" depends on ARCH_OMAP2PLUS diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile index 863fd18..d1b0832 100644 --- a/drivers/cpufreq/Makefile +++ b/drivers/cpufreq/Makefile @@ -44,6 +44,10 @@ obj-$(CONFIG_X86_INTEL_PSTATE) += intel_pstate.o ################################################################################## # ARM SoC drivers +obj-$(CONFIG_ARM_BIG_LITTLE_CPUFREQ) += arm_big_little.o +# big LITTLE per platform glues. Keep DT_BL_CPUFREQ as the last entry in all big +# LITTLE drivers, so that it is probed last. +obj-$(CONFIG_ARM_DT_BL_CPUFREQ) += arm_big_little_dt.o obj-$(CONFIG_UX500_SOC_DB8500) += dbx500-cpufreq.o obj-$(CONFIG_ARM_S3C2416_CPUFREQ) += s3c2416-cpufreq.o obj-$(CONFIG_ARM_S3C64XX_CPUFREQ) += s3c64xx-cpufreq.o diff --git a/drivers/cpufreq/arm_big_little.c b/drivers/cpufreq/arm_big_little.c new file mode 100644 index 0000000..1d29d1a --- /dev/null +++ b/drivers/cpufreq/arm_big_little.c @@ -0,0 +1,282 @@ +/*
- ARM big.LITTLE Platforms CPUFreq support
What is specific to bL? This looks like just a multi-cluster cpufreq driver and should be generalized to that. Also, why can't the existing cpufreq-cpu0 driver be extended to support this?
- Copyright (C) 2013 ARM Ltd.
- Sudeep KarkadaNagesha sudeep.karkadanagesha@arm.com
- Copyright (C) 2013 Linaro.
- Viresh Kumar viresh.kumar@linaro.org
- 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/clk.h> +#include <linux/cpu.h> +#include <linux/cpufreq.h> +#include <linux/cpumask.h> +#include <linux/export.h> +#include <linux/of_platform.h> +#include <linux/opp.h> +#include <linux/slab.h> +#include <linux/topology.h> +#include <linux/types.h>
+#include "arm_big_little.h"
+/* Currently we support only two clusters */ +#define MAX_CLUSTERS 2
Why? Because that is what the define is or there are other limitations? Seems like this could and should be dynamically discovered with DT.
Rob