[PATCH RFC] WIP: clk: Draft for BCM2835 ARM core frequency control

[Stefan Wahren]

Disclaimer: DO NOT USE THIS UNTESTED CODE !!!

This approach adds a new clock driver which controls the ARM core
frequency via the mailbox interface. So the cpufreq-dt driver can
operate via the common clock API.

Signed-off-by: Stefan Wahren <***@i2se.com>
---
arch/arm/boot/dts/bcm2835-rpi.dtsi | 7 ++
arch/arm/boot/dts/bcm2837.dtsi | 26 ++++++++
drivers/clk/bcm/Kconfig | 8 +++
drivers/clk/bcm/Makefile | 1 +
drivers/clk/bcm/clk-raspberrypi.c | 130 +++++++++++++++++++++++++++++++++++++
5 files changed, 172 insertions(+)
create mode 100644 drivers/clk/bcm/clk-raspberrypi.c

diff --git a/arch/arm/boot/dts/bcm2835-rpi.dtsi b/arch/arm/boot/dts/bcm2835-rpi.dtsi
index 6c3cfaa..e6d1627 100644
--- a/arch/arm/boot/dts/bcm2835-rpi.dtsi
+++ b/arch/arm/boot/dts/bcm2835-rpi.dtsi
@@ -35,6 +35,13 @@
reg = <0x7e00b840 0xf>;
interrupts = <0 2>;
};
+
+ arm_clk: arm_clk {
+ compatible = "raspberrypi,bcm2835-cpu";
+ clocks = <&clocks BCM2835_CLOCK_VPU>;
+ #clock-cells = <0>;
+ clock-output-names = "arm";
+ };
};
};

diff --git a/arch/arm/boot/dts/bcm2837.dtsi b/arch/arm/boot/dts/bcm2837.dtsi
index 7704bb0..faabc55 100644
--- a/arch/arm/boot/dts/bcm2837.dtsi
+++ b/arch/arm/boot/dts/bcm2837.dtsi
@@ -38,6 +38,9 @@
reg = <0>;
enable-method = "spin-table";
cpu-release-addr = <0x0 0x000000d8>;
+ clocks = <&arm_clk>;
+ clock-names = "cpu";
+ operating-points-v2 = <&cpu0_opp_table>;
};

cpu1: ***@1 {
@@ -46,6 +49,9 @@
reg = <1>;
enable-method = "spin-table";
cpu-release-addr = <0x0 0x000000e0>;
+ clocks = <&arm_clk>;
+ clock-names = "cpu";
+ operating-points-v2 = <&cpu0_opp_table>;
};

cpu2: ***@2 {
@@ -54,6 +60,9 @@
reg = <2>;
enable-method = "spin-table";
cpu-release-addr = <0x0 0x000000e8>;
+ clocks = <&arm_clk>;
+ clock-names = "cpu";
+ operating-points-v2 = <&cpu0_opp_table>;
};

cpu3: ***@3 {
@@ -62,6 +71,23 @@
reg = <3>;
enable-method = "spin-table";
cpu-release-addr = <0x0 0x000000f0>;
+ clocks = <&arm_clk>;
+ clock-names = "cpu";
+ operating-points-v2 = <&cpu0_opp_table>;
+ };
+
+ cpu0_opp_table: opp_table0 {
+ compatible = "operating-points-v2";
+ opp-shared;
+
+ ***@600000000 {
+ opp-hz = /bits/ 64 <600000000>;
+ opp-suspend;
+ };
+
+ ***@1200000000 {
+ opp-hz = /bits/ 64 <1200000000>;
+ };
};
};
};
diff --git a/drivers/clk/bcm/Kconfig b/drivers/clk/bcm/Kconfig
index 4c4bd85..3aaabe7 100644
--- a/drivers/clk/bcm/Kconfig
+++ b/drivers/clk/bcm/Kconfig
@@ -63,3 +63,11 @@ config CLK_BCM_SR
default ARCH_BCM_IPROC
help
Enable common clock framework support for the Broadcom Stingray SoC
+
+config CLK_RASPBERRYPI_CPU
+ bool "Raspberry Pi CPU clock driver"
+ depends on ARCH_BCM2835 || (COMPILE_TEST && OF)
+ depends on RASPBERRYPI_FIRMWARE=y
+ help
+ This enables support for the RPi CPU clock which can be adjusted
+ via the RPi firmware.
diff --git a/drivers/clk/bcm/Makefile b/drivers/clk/bcm/Makefile
index 002661d..b5025eb 100644
--- a/drivers/clk/bcm/Makefile
+++ b/drivers/clk/bcm/Makefile
@@ -7,6 +7,7 @@ obj-$(CONFIG_CLK_BCM_KONA) += clk-bcm21664.o
obj-$(CONFIG_COMMON_CLK_IPROC) += clk-iproc-armpll.o clk-iproc-pll.o clk-iproc-asiu.o
obj-$(CONFIG_ARCH_BCM2835) += clk-bcm2835.o
obj-$(CONFIG_ARCH_BCM2835) += clk-bcm2835-aux.o
+obj-$(CONFIG_CLK_RASPBERRYPI_CPU) += clk-raspberrypi.o
obj-$(CONFIG_ARCH_BCM_53573) += clk-bcm53573-ilp.o
obj-$(CONFIG_CLK_BCM_CYGNUS) += clk-cygnus.o
obj-$(CONFIG_CLK_BCM_HR2) += clk-hr2.o
diff --git a/drivers/clk/bcm/clk-raspberrypi.c b/drivers/clk/bcm/clk-raspberrypi.c
new file mode 100644
index 0000000..d629744
--- /dev/null
+++ b/drivers/clk/bcm/clk-raspberrypi.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Raspberry Pi CPU clock driver
+ *
+ * Copyright (C) 2018 Stefan Wahren <***@i2se.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <soc/bcm2835/raspberrypi-firmware.h>
+
+#define VCMSG_ID_ARM_CLOCK 0x000000003 /* Clock/Voltage ID's */
+
+struct rpi_cpu_clkgen {
+ struct clk_hw hw;
+ struct rpi_firmware *fw;
+};
+
+static int rpi_cpu_clock_property(struct rpi_firmware *fw, u32 tag, u32 *val)
+{
+ struct {
+ u32 id;
+ u32 val;
+ } packet;
+ int ret;
+
+ packet.id = VCMSG_ID_ARM_CLOCK;
+ packet.val = *val;
+ ret = rpi_firmware_property(fw, tag, &packet, sizeof(packet));
+ if (ret)
+ return ret;
+
+ *val = packet.val;
+
+ return 0;
+}
+
+static unsigned long rpi_cpu_get_rate(struct clk_hw *hw,
+ unsigned long parent_rate)
+{
+ struct rpi_cpu_clkgen *cpu = container_of(hw, struct rpi_cpu_clkgen, hw);
+ u32 rate = 0;
+
+ rpi_cpu_clock_property(cpu->fw, RPI_FIRMWARE_GET_CLOCK_RATE, &rate);
+
+ return rate;
+}
+
+static long rpi_cpu_round_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long *parent_rate)
+{
+ return rate;
+}
+
+static int rpi_cpu_set_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long parent_rate)
+{
+ struct rpi_cpu_clkgen *cpu = container_of(hw, struct rpi_cpu_clkgen, hw);
+ u32 new_rate = rate;
+
+ return rpi_cpu_clock_property(cpu->fw, RPI_FIRMWARE_SET_CLOCK_RATE,
+ &new_rate);
+}
+
+static const struct clk_ops rpi_cpu_ops = {
+ .recalc_rate = rpi_cpu_get_rate,
+ .round_rate = rpi_cpu_round_rate,
+ .set_rate = rpi_cpu_set_rate,
+};
+
+static int rpi_cpu_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device_node *fw_node;
+ struct rpi_cpu_clkgen *cpu;
+ struct clk_init_data init;
+ int ret;
+
+ cpu = devm_kzalloc(dev, sizeof(*cpu), GFP_KERNEL);
+ if (!cpu)
+ return -ENOMEM;
+
+ fw_node = of_find_compatible_node(NULL, NULL,
+ "raspberrypi,bcm2835-firmware");
+ if (!fw_node) {
+ dev_err(dev, "Missing firmware node\n");
+ return -ENOENT;
+ }
+
+ cpu->fw = rpi_firmware_get(fw_node);
+ of_node_put(fw_node);
+ if (!cpu->fw)
+ return -EPROBE_DEFER;
+
+ init.name = pdev->dev.of_node->name;
+ init.ops = &rpi_cpu_ops;
+
+ cpu->hw.init = &init;
+ ret = devm_clk_hw_register(&pdev->dev, &cpu->hw);
+ if (ret)
+ return ret;
+
+ return of_clk_add_hw_provider(pdev->dev.of_node, of_clk_hw_simple_get,
+ &cpu->hw);
+}
+
+static const struct of_device_id rpi_cpu_of_match[] = {
+ { .compatible = "raspberrypi,bcm2835-cpu", },
+ {},
+};
+MODULE_DEVICE_TABLE(of, rpi_cpu_of_match);
+
+static struct platform_driver rpi_cpu_driver = {
+ .driver = {
+ .name = "raspberrypi-cpu",
+ .of_match_table = rpi_cpu_of_match,
+ },
+ .probe = rpi_cpu_probe,
+};
+builtin_platform_driver(rpi_cpu_driver);
+
+MODULE_AUTHOR("Stefan Wahren <***@i2se.com>");
+MODULE_DESCRIPTION("Raspberry Pi CPU clock driver");
+MODULE_LICENSE("GPL v2");

[Eric Anholt]

Post by Stefan Wahren
Disclaimer: DO NOT USE THIS UNTESTED CODE !!!
This approach adds a new clock driver which controls the ARM core
frequency via the mailbox interface. So the cpufreq-dt driver can
operate via the common clock API.

I've tried to follow the logic in the FW related to clock management
again, and once again I'm going to admit defeat. So here are a couple
of things I learned:

I suspect you're going to have a very restricted frequency range if you
don't send a SET_TURBO packet or have a turbo setting in config.txt
already. (GET_TURBO returns that state).

Also, if GET_MAX_TEMPERATURE returns nonzero, that means there's a VPU
thread running that's polling the temp and voltage and will crank down
the voltage and ARM/V3D/CORE/ISP/SDRAM clocks when out of bounds.

[Sergey Suloev]

Hi Stefan

Post by Stefan Wahren
Disclaimer: DO NOT USE THIS UNTESTED CODE !!!
This approach adds a new clock driver which controls the ARM core
frequency via the mailbox interface. So the cpufreq-dt driver can
operate via the common clock API.
---
arch/arm/boot/dts/bcm2835-rpi.dtsi | 7 ++
arch/arm/boot/dts/bcm2837.dtsi | 26 ++++++++
drivers/clk/bcm/Kconfig | 8 +++
drivers/clk/bcm/Makefile | 1 +
drivers/clk/bcm/clk-raspberrypi.c | 130 +++++++++++++++++++++++++++++++++++++
5 files changed, 172 insertions(+)
create mode 100644 drivers/clk/bcm/clk-raspberrypi.c
diff --git a/arch/arm/boot/dts/bcm2835-rpi.dtsi b/arch/arm/boot/dts/bcm2835-rpi.dtsi
index 6c3cfaa..e6d1627 100644
--- a/arch/arm/boot/dts/bcm2835-rpi.dtsi
+++ b/arch/arm/boot/dts/bcm2835-rpi.dtsi
@@ -35,6 +35,13 @@
reg = <0x7e00b840 0xf>;
interrupts = <0 2>;
};
+
+ arm_clk: arm_clk {
+ compatible = "raspberrypi,bcm2835-cpu";
+ clocks = <&clocks BCM2835_CLOCK_VPU>;
+ #clock-cells = <0>;
+ clock-output-names = "arm";
+ };
};
};
diff --git a/arch/arm/boot/dts/bcm2837.dtsi b/arch/arm/boot/dts/bcm2837.dtsi
index 7704bb0..faabc55 100644
--- a/arch/arm/boot/dts/bcm2837.dtsi
+++ b/arch/arm/boot/dts/bcm2837.dtsi
@@ -38,6 +38,9 @@
reg = <0>;
enable-method = "spin-table";
cpu-release-addr = <0x0 0x000000d8>;
+ clocks = <&arm_clk>;
+ clock-names = "cpu";
+ operating-points-v2 = <&cpu0_opp_table>;
};
@@ -46,6 +49,9 @@
reg = <1>;
enable-method = "spin-table";
cpu-release-addr = <0x0 0x000000e0>;
+ clocks = <&arm_clk>;
+ clock-names = "cpu";
+ operating-points-v2 = <&cpu0_opp_table>;
};
@@ -54,6 +60,9 @@
reg = <2>;
enable-method = "spin-table";
cpu-release-addr = <0x0 0x000000e8>;
+ clocks = <&arm_clk>;
+ clock-names = "cpu";
+ operating-points-v2 = <&cpu0_opp_table>;
};
@@ -62,6 +71,23 @@
reg = <3>;
enable-method = "spin-table";
cpu-release-addr = <0x0 0x000000f0>;
+ clocks = <&arm_clk>;
+ clock-names = "cpu";
+ operating-points-v2 = <&cpu0_opp_table>;
+ };
+
+ cpu0_opp_table: opp_table0 {
+ compatible = "operating-points-v2";
+ opp-shared;
+
+ opp-hz = /bits/ 64 <600000000>;
+ opp-suspend;
+ };
+
+ opp-hz = /bits/ 64 <1200000000>;
+ };
};
};
};
diff --git a/drivers/clk/bcm/Kconfig b/drivers/clk/bcm/Kconfig
index 4c4bd85..3aaabe7 100644
--- a/drivers/clk/bcm/Kconfig
+++ b/drivers/clk/bcm/Kconfig
@@ -63,3 +63,11 @@ config CLK_BCM_SR
default ARCH_BCM_IPROC
help
Enable common clock framework support for the Broadcom Stingray SoC
+
+config CLK_RASPBERRYPI_CPU
+ bool "Raspberry Pi CPU clock driver"
+ depends on ARCH_BCM2835 || (COMPILE_TEST && OF)
+ depends on RASPBERRYPI_FIRMWARE=y
+ help
+ This enables support for the RPi CPU clock which can be adjusted
+ via the RPi firmware.
diff --git a/drivers/clk/bcm/Makefile b/drivers/clk/bcm/Makefile
index 002661d..b5025eb 100644
--- a/drivers/clk/bcm/Makefile
+++ b/drivers/clk/bcm/Makefile
@@ -7,6 +7,7 @@ obj-$(CONFIG_CLK_BCM_KONA) += clk-bcm21664.o
obj-$(CONFIG_COMMON_CLK_IPROC) += clk-iproc-armpll.o clk-iproc-pll.o clk-iproc-asiu.o
obj-$(CONFIG_ARCH_BCM2835) += clk-bcm2835.o
obj-$(CONFIG_ARCH_BCM2835) += clk-bcm2835-aux.o
+obj-$(CONFIG_CLK_RASPBERRYPI_CPU) += clk-raspberrypi.o
obj-$(CONFIG_ARCH_BCM_53573) += clk-bcm53573-ilp.o
obj-$(CONFIG_CLK_BCM_CYGNUS) += clk-cygnus.o
obj-$(CONFIG_CLK_BCM_HR2) += clk-hr2.o
diff --git a/drivers/clk/bcm/clk-raspberrypi.c b/drivers/clk/bcm/clk-raspberrypi.c
new file mode 100644
index 0000000..d629744
--- /dev/null
+++ b/drivers/clk/bcm/clk-raspberrypi.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Raspberry Pi CPU clock driver
+ *
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <soc/bcm2835/raspberrypi-firmware.h>
+
+#define VCMSG_ID_ARM_CLOCK 0x000000003 /* Clock/Voltage ID's */
+
+struct rpi_cpu_clkgen {
+ struct clk_hw hw;
+ struct rpi_firmware *fw;
+};
+
+static int rpi_cpu_clock_property(struct rpi_firmware *fw, u32 tag, u32 *val)
+{
+ struct {
+ u32 id;
+ u32 val;
+ } packet;
+ int ret;
+
+ packet.id = VCMSG_ID_ARM_CLOCK;
+ packet.val = *val;
+ ret = rpi_firmware_property(fw, tag, &packet, sizeof(packet));
+ if (ret)
+ return ret;
+
+ *val = packet.val;
+
+ return 0;
+}
+
+static unsigned long rpi_cpu_get_rate(struct clk_hw *hw,
+ unsigned long parent_rate)
+{
+ struct rpi_cpu_clkgen *cpu = container_of(hw, struct rpi_cpu_clkgen, hw);
+ u32 rate = 0;
+
+ rpi_cpu_clock_property(cpu->fw, RPI_FIRMWARE_GET_CLOCK_RATE, &rate);
+
+ return rate;
+}
+
+static long rpi_cpu_round_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long *parent_rate)
+{
+ return rate;
+}
+
+static int rpi_cpu_set_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long parent_rate)
+{
+ struct rpi_cpu_clkgen *cpu = container_of(hw, struct rpi_cpu_clkgen, hw);
+ u32 new_rate = rate;
+
+ return rpi_cpu_clock_property(cpu->fw, RPI_FIRMWARE_SET_CLOCK_RATE,
+ &new_rate);
+}
+
+static const struct clk_ops rpi_cpu_ops = {
+ .recalc_rate = rpi_cpu_get_rate,
+ .round_rate = rpi_cpu_round_rate,
+ .set_rate = rpi_cpu_set_rate,
+};
+
+static int rpi_cpu_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device_node *fw_node;
+ struct rpi_cpu_clkgen *cpu;
+ struct clk_init_data init;
+ int ret;
+
+ cpu = devm_kzalloc(dev, sizeof(*cpu), GFP_KERNEL);
+ if (!cpu)
+ return -ENOMEM;
+
+ fw_node = of_find_compatible_node(NULL, NULL,
+ "raspberrypi,bcm2835-firmware");
+ if (!fw_node) {
+ dev_err(dev, "Missing firmware node\n");
+ return -ENOENT;
+ }
+
+ cpu->fw = rpi_firmware_get(fw_node);
+ of_node_put(fw_node);
+ if (!cpu->fw)
+ return -EPROBE_DEFER;
+
+ init.name = pdev->dev.of_node->name;
+ init.ops = &rpi_cpu_ops;
+
+ cpu->hw.init = &init;
+ ret = devm_clk_hw_register(&pdev->dev, &cpu->hw);
+ if (ret)
+ return ret;
+
+ return of_clk_add_hw_provider(pdev->dev.of_node, of_clk_hw_simple_get,
+ &cpu->hw);
+}
+
+static const struct of_device_id rpi_cpu_of_match[] = {
+ { .compatible = "raspberrypi,bcm2835-cpu", },
+ {},
+};
+MODULE_DEVICE_TABLE(of, rpi_cpu_of_match);
+
+static struct platform_driver rpi_cpu_driver = {
+ .driver = {
+ .name = "raspberrypi-cpu",
+ .of_match_table = rpi_cpu_of_match,
+ },
+ .probe = rpi_cpu_probe,
+};
+builtin_platform_driver(rpi_cpu_driver);
+
+MODULE_DESCRIPTION("Raspberry Pi CPU clock driver");
+MODULE_LICENSE("GPL v2");

I tried your patch with Rpi3 and there is a crash at boot. Didn't you
forget anything important ?