[RFC PATCH 0/2] Add Krait Cache Scaling support

[RFC PATCH 0/2] Add Krait Cache Scaling support

[Ansuel Smith]

This adds Krait Cache scaling support using the cpufreq notifier.
I have some doubt about where this should be actually placed (clk or cpufreq)?
Also the original idea was to create a dedicated cpufreq driver (like it's done in
the codeaurora qcom repo) by copying the cpufreq-dt driver and adding the cache
scaling logic but i still don't know what is better. Have a very similar driver or
add a dedicated driver only for the cache using the cpufreq notifier and do the
scale on every freq transition.
Thanks to everyone who will review or answer these questions.

Ansuel Smith (2):
  cpufreq: qcom: Add Krait Cache Scaling support
  dt-bindings: cpufreq: Document Krait CPU Cache scaling

 .../bindings/cpufreq/krait-cache-scale.yaml   |  89 ++++++++
 drivers/cpufreq/Kconfig.arm                   |   9 +
 drivers/cpufreq/Makefile                      |   1 +
 drivers/cpufreq/krait-cache.c                 | 216 ++++++++++++++++++
 4 files changed, 315 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/cpufreq/krait-cache-scale.yaml
 create mode 100644 drivers/cpufreq/krait-cache.c

-- 
2.27.0

[RFC PATCH 1/2] cpufreq: qcom: Add Krait Cache Scaling support

[Ansuel Smith]

Qcom Krait CPUs use the generic cpufreq-dt driver and doesn't actually
scale the Cache frequency when the CPU frequency is changed. This
companion driver register with the cpu notifier and scale the Cache
based on the max Freq across all core as the CPU cache is shared across
all of them. If provided this also scale the voltage of the regulator
attached to the CPU cache. The scaling logic is based on the CPU freq
and the 3 scaling interval are set by the device dts.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
---
 drivers/cpufreq/Kconfig.arm   |   9 ++
 drivers/cpufreq/Makefile      |   1 +
 drivers/cpufreq/krait-cache.c | 218 ++++++++++++++++++++++++++++++++++
 3 files changed, 228 insertions(+)
 create mode 100644 drivers/cpufreq/krait-cache.c

diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index c6cbfc8baf72..4ed5e73051df 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -126,6 +126,15 @@ config ARM_OMAP2PLUS_CPUFREQ
 	depends on ARCH_OMAP2PLUS
 	default ARCH_OMAP2PLUS
 
+config ARM_QCOM_KRAIT_CACHE_SCALE
+	tristate "Scaling support for Krait CPU Cache"
+	depends on ARCH_QCOM || COMPILE_TEST
+	help
+	  This adds the Scaling support for the Krait CPU Cache shared by
+	  all cores.
+
+	  If in doubt, say N.
+
 config ARM_QCOM_CPUFREQ_NVMEM
 	tristate "Qualcomm nvmem based CPUFreq"
 	depends on ARCH_QCOM
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index f6670c4abbb0..eee53d7e8b09 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -61,6 +61,7 @@ obj-$(CONFIG_MACH_MVEBU_V7)		+= mvebu-cpufreq.o
 obj-$(CONFIG_ARM_OMAP2PLUS_CPUFREQ)	+= omap-cpufreq.o
 obj-$(CONFIG_ARM_PXA2xx_CPUFREQ)	+= pxa2xx-cpufreq.o
 obj-$(CONFIG_PXA3xx)			+= pxa3xx-cpufreq.o
+obj-$(CONFIG_ARM_QCOM_KRAIT_CACHE_SCALE) += krait-cache.o
 obj-$(CONFIG_ARM_QCOM_CPUFREQ_HW)	+= qcom-cpufreq-hw.o
 obj-$(CONFIG_ARM_QCOM_CPUFREQ_NVMEM)	+= qcom-cpufreq-nvmem.o
 obj-$(CONFIG_ARM_RASPBERRYPI_CPUFREQ) 	+= raspberrypi-cpufreq.o
diff --git a/drivers/cpufreq/krait-cache.c b/drivers/cpufreq/krait-cache.c
new file mode 100644
index 000000000000..77cdd2cb22fc
--- /dev/null
+++ b/drivers/cpufreq/krait-cache.c
@@ -0,0 +1,218 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/cpufreq.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/clk.h>
+#include <linux/slab.h>
+#include <linux/regulator/consumer.h>
+
+struct krait_data {
+	struct clk *l2_clk; /* L2 clock */
+	unsigned int l2_volt_tol; /* L2 voltage tolerance */
+
+	struct regulator *l2_regulator; /* L2 supply */
+	unsigned int l2_rate[3]; /* L2 bus clock rate */
+	bool l2_rate_set;
+
+	unsigned int l2_cpufreq[3]; /* L2 target CPU frequency */
+	unsigned int l2_volt[3]; /* L2 voltage array */
+
+	unsigned long curr_l2_freq;
+	unsigned long curr_l2_volt;
+
+	struct notifier_block nb;
+};
+
+static int krait_cache_notifier(struct notifier_block *nb, unsigned long cmd,
+				void *v)
+{
+	struct cpufreq_freqs *freqs = (struct cpufreq_freqs *)v;
+	unsigned long l2_freq, target_l2_freq;
+	unsigned long l2_vol, target_l2_volt;
+	struct regulator *l2_regulator;
+	struct krait_data *data;
+	struct clk *l2_clk;
+	int ret = 0;
+
+	data = container_of(nb, struct krait_data, nb);
+
+	if (cmd == CPUFREQ_PRECHANGE) {
+		unsigned int target_freq = freqs->new;
+		int cpu, cur_cpu = freqs->policy->cpu, l2_index, tol = 0;
+
+		l2_clk = data->l2_clk;
+
+		/* find the max freq across all core */
+		for_each_present_cpu(cpu)
+			if (cpu != cur_cpu)
+				target_freq = max(target_freq,
+						  cpufreq_quick_get(cpu));
+
+		/* find l2_freq and l2_volt  */
+		for (l2_index = 0;
+		     l2_index < 2 && target_freq <= data->l2_cpufreq[l2_index];
+		     l2_index++)
+			break;
+
+		l2_freq = data->curr_l2_freq;
+		target_l2_freq = data->l2_rate[l2_index];
+
+		/* scale only if needed */
+		if (l2_freq != target_l2_freq) {
+			/*
+			 * Set to idle bin if switching from normal to high bin
+			 * or vice versa. It has been notice that a bug is triggered
+			 * in cache scaling when more than one bin is scaled, to fix
+			 * this we first need to transition to the base rate and then
+			 * to target rate
+			 */
+			if ((l2_index == 2 && l2_freq == data->l2_rate[1]) ||
+			    (l2_index == 1 && l2_freq == data->l2_rate[2])) {
+				ret = clk_set_rate(l2_clk, data->l2_rate[0]);
+				if (ret)
+					goto exit;
+			}
+
+			ret = clk_set_rate(l2_clk, target_l2_freq);
+			if (ret)
+				goto exit;
+
+			data->curr_l2_freq = target_l2_freq;
+
+			l2_regulator = data->l2_regulator;
+			if (l2_regulator) {
+				l2_vol = data->curr_l2_volt;
+				target_l2_volt = data->l2_volt[l2_index];
+
+				if (l2_vol != target_l2_volt) {
+					tol = target_l2_volt *
+					      data->l2_volt_tol / 100;
+					ret = regulator_set_voltage_tol(
+						l2_regulator, target_l2_volt,
+						tol);
+					if (ret)
+						goto exit;
+
+					data->curr_l2_volt = target_l2_volt;
+				}
+			}
+		}
+	}
+
+exit:
+	return notifier_from_errno(ret);
+}
+
+static int krait_cache_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct clk *l2_clk;
+	struct device_node *vdd;
+	struct krait_data *data;
+	struct regulator *l2_regulator;
+	struct device *dev = &pdev->dev;
+	struct device_node *node = dev->of_node;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->l2_clk = clk_get(dev, "l2");
+	if (IS_ERR(l2_clk)) {
+		ret = PTR_ERR(l2_clk);
+		goto err;
+	}
+
+	of_property_read_u32(node, "voltage-tolerance", &data->l2_volt_tol);
+
+	of_property_read_u32_array(node, "l2-rates", data->l2_rate, 3);
+	if (data->l2_rate[0] && data->l2_rate[1] && data->l2_rate[2]) {
+		data->l2_rate_set = true;
+		of_property_read_u32_array(node, "l2-cpufreq", data->l2_cpufreq,
+					   3);
+		of_property_read_u32_array(node, "l2-volt", data->l2_volt, 3);
+	} else {
+		dev_warn(dev, "failed to parse L2 rates\n");
+	}
+
+	if (!data->l2_cpufreq[0] && !data->l2_cpufreq[1] &&
+	    !data->l2_cpufreq[2] && data->l2_rate_set) {
+		int i;
+
+		dev_warn(dev,
+			 "failed to parse target cpu freq, using defaults\n");
+		for (i = 0; i < 3; i++)
+			data->l2_cpufreq[i] = data->l2_rate[i];
+	}
+
+	if (data->l2_volt[0] && data->l2_volt[1] && data->l2_volt[2] &&
+	    data->l2_rate_set) {
+		vdd = of_parse_phandle(node, "l2-supply", 0);
+
+		if (vdd) {
+			l2_regulator = devm_regulator_get(dev, vdd->name);
+			if (!IS_ERR(l2_regulator)) {
+				data->l2_regulator = l2_regulator;
+			} else {
+				dev_err(dev,
+					"failed to get l2 supply, error=%pe\n",
+					l2_regulator);
+			}
+
+			of_node_put(vdd);
+		}
+	}
+
+	platform_set_drvdata(pdev, data);
+
+	data->nb.notifier_call = krait_cache_notifier;
+	cpufreq_register_notifier(&data->nb, CPUFREQ_TRANSITION_NOTIFIER);
+
+	return 0;
+
+err:
+	kfree(data);
+	return ret;
+}
+
+static int krait_cache_remove(struct platform_device *pdev)
+{
+	struct krait_data *data = platform_get_drvdata(pdev);
+
+	cpufreq_unregister_notifier(&data->nb, CPUFREQ_TRANSITION_NOTIFIER);
+
+	return 0;
+}
+
+static const struct of_device_id krait_cache_match_table[] = {
+	{ .compatible = "qcom,krait-cache" },
+	{}
+};
+
+static struct platform_driver krait_cache_driver = {
+	.probe		= krait_cache_probe,
+	.remove		= krait_cache_remove,
+	.driver		= {
+		.name   = "krait-cache-scaling",
+		.of_match_table = krait_cache_match_table,
+	},
+};
+
+static int __init krait_cache_init(void)
+{
+	return platform_driver_register(&krait_cache_driver);
+}
+late_initcall(krait_cache_init);
+
+static void __exit krait_cache_exit(void)
+{
+	platform_driver_unregister(&krait_cache_driver);
+}
+module_exit(krait_cache_exit);
+
+MODULE_DESCRIPTION("Krait CPU Cache Scaling driver");
+MODULE_LICENSE("GPL v2");
-- 
2.27.0

[RFC PATCH 2/2] dt-bindings: cpufreq: Document Krait CPU Cache scaling

[Ansuel Smith]

Document dedicated Krait CPU Cache Scaling driver.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
---
 .../bindings/cpufreq/krait-cache-scale.yaml   | 89 +++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/cpufreq/krait-cache-scale.yaml

diff --git a/Documentation/devicetree/bindings/cpufreq/krait-cache-scale.yaml b/Documentation/devicetree/bindings/cpufreq/krait-cache-scale.yaml
new file mode 100644
index 000000000000..190276ba035a
--- /dev/null
+++ b/Documentation/devicetree/bindings/cpufreq/krait-cache-scale.yaml
@@ -0,0 +1,89 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/cpufreq/krait-cache-scale.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Krait Cpu Cache Frequency Scaling dedicated driver
+
+maintainers:
+  - Ansuel Smith <ansuelsmth@gmail.com>
+
+description: |
+  This Scale the Krait CPU Cache Frequency and optionally voltage
+  when the Cpu Frequency is changed (using the cpufreq notifier).
+
+  Cache is scaled with the max frequency across all core and the cache
+  frequency will scale based on the configured threshold in the dts.
+
+  The cache is hardcoded to 3 frequency bin, idle, nominal and high.
+
+properties:
+  compatible:
+    const: qcom,krait-cache
+
+  clocks:
+    description: Phandle to the L2 CPU clock
+
+  clock-names:
+    const: "l2"
+
+  voltage-tolerance:
+    description: Same voltage tollerance of the Krait CPU
+
+  l2-rates:
+    description: |
+      Frequency the L2 cache will be scaled at.
+      Value is in Hz.
+    items:
+      - description: idle
+      - description: nominal
+      - description: high
+
+  l2-cpufreq:
+    description: |
+      Threshold used by the driver to scale the L2 cache.
+      If the max CPU Frequency is more than the set frequency,
+      the driver will transition to the next frequency bin.
+      Value is in kHz
+    items:
+      - description: idle
+      - description: nominal
+      - description: high
+
+  l2-volt:
+    description: |
+      Threshold used by the driver to scale the L2 cache.
+      If the max CPU Frequency is more than the set frequency,
+      the driver will transition to the next frequency bin.
+      Value is in microvolt.
+    items:
+      - description: idle
+      - description: nominal
+      - description: high
+
+  l2-supply:
+    description: Phandle to the L2 regulator supply.
+
+required:
+  - compatible
+  - clocks
+  - clock-names
+  - voltage-tolerance
+  - l2-rates
+  - l2-cpufreq
+  - l2-supply
+  - l2-volt
+
+examples:
+  - |
+    qcom-krait-cache {
+      compatible = "qcom,krait-cache";
+      clocks = <&kraitcc 4>;
+      clock-names = "l2";
+      voltage-tolerance = <5>;
+      l2-rates = <384000000 1000000000 1200000000>;
+      l2-cpufreq = <384000 600000 1200000>;
+      l2-volt = <1100000 1100000 1150000>;
+      l2-supply = <&smb208_s1a>;
+    };
-- 
2.27.0

Re: [RFC PATCH 2/2] dt-bindings: cpufreq: Document Krait CPU Cache scaling

[Rob Herring]

On Wed, 05 Aug 2020 15:11:59 +0200, Ansuel Smith wrote:
> Document dedicated Krait CPU Cache Scaling driver.
> 
> Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
> ---
>  .../bindings/cpufreq/krait-cache-scale.yaml   | 89 +++++++++++++++++++
>  1 file changed, 89 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/cpufreq/krait-cache-scale.yaml
> 


My bot found errors running 'make dt_binding_check' on your patch:

/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/cpufreq/krait-cache-scale.example.dt.yaml: qcom-krait-cache: l2-cpufreq: [[384000, 600000, 1200000]] is too short
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/cpufreq/krait-cache-scale.example.dt.yaml: qcom-krait-cache: l2-rates: [[384000000, 1000000000, 1200000000]] is too short
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/cpufreq/krait-cache-scale.example.dt.yaml: qcom-krait-cache: l2-volt: [[1100000, 1100000, 1150000]] is too short


See https://patchwork.ozlabs.org/patch/1341295

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure dt-schema is up to date:

pip3 install git+https://github.com/devicetree-org/dt-schema.git@master --upgrade

Please check and re-submit.