[RFC PATCH v2 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@xxxxxxxxx>
---
 drivers/cpufreq/Kconfig.arm   |   9 ++
 drivers/cpufreq/Makefile      |   1 +
 drivers/cpufreq/krait-cache.c | 213 ++++++++++++++++++++++++++++++++++
 3 files changed, 223 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..a2a14eb38dc0
--- /dev/null
+++ b/drivers/cpufreq/krait-cache.c
@@ -0,0 +1,213 @@
+// 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 */
+
+	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)
+{
+	unsigned int target_freq, cpu, cur_cpu, l2_index, tol;
+	unsigned long curr_l2_freq, target_l2_freq;
+	unsigned long curr_l2_vol, target_l2_volt;
+	struct cpufreq_freqs *freqs;
+	struct krait_data *data;
+	struct clk *l2_clk;
+	int ret = 0;
+
+	if (cmd == CPUFREQ_PRECHANGE) {
+		freqs = (struct cpufreq_freqs *)v;
+		target_freq = freqs->new;
+		cur_cpu = freqs->policy->cpu;
+
+		data = container_of(nb, struct krait_data, nb);
+
+		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;
+
+		curr_l2_freq = data->curr_l2_freq;
+		target_l2_freq = data->l2_rate[l2_index];
+
+		/* scale only if needed */
+		if (curr_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 (likely(l2_index > 0 &&
+				   curr_l2_freq != data->l2_rate[0])) {
+				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;
+
+			curr_l2_vol = data->curr_l2_volt;
+			target_l2_volt = data->l2_volt[l2_index];
+
+			if (curr_l2_vol != target_l2_volt) {
+				tol = target_l2_volt * data->l2_volt_tol / 100;
+				ret = regulator_set_voltage_tol(
+					data->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 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 exit;
+	}
+
+	ret = of_property_read_u32(node, "voltage-tolerance",
+				   &data->l2_volt_tol);
+	if (ret) {
+		dev_err(dev, "missing voltage tolerance\n");
+		goto exit;
+	}
+
+	ret = of_property_read_u32_array(node, "l2-rates", data->l2_rate, 3);
+	if (ret) {
+		dev_err(dev, "failed to parse L2 rates\n");
+		goto exit;
+	}
+
+	ret = of_property_read_u32_array(node, "l2-cpufreq", data->l2_cpufreq,
+					 3);
+	if (ret) {
+		dev_err(dev, "failed to parse L2 cpufreq range\n");
+		goto exit;
+	}
+
+	ret = of_property_read_u32_array(node, "l2-volt", data->l2_volt, 3);
+	if (ret) {
+		dev_err(dev, "failed to parse L2 volt range\n");
+		goto exit;
+	}
+
+	vdd = of_parse_phandle(node, "l2-supply", 0);
+	if (!vdd) {
+		dev_err(dev, "missing L2 supply\n");
+		ret = -EINVAL;
+		goto exit;
+	}
+
+	data->l2_regulator = devm_regulator_get(dev, vdd->name);
+	if (IS_ERR(data->l2_regulator)) {
+		dev_err(dev, "failed to get l2 supply, error=%pe\n",
+			data->l2_regulator);
+		ret = PTR_ERR(data->l2_regulator);
+		goto exit_vdd;
+	}
+
+	platform_set_drvdata(pdev, data);
+
+	data->nb.notifier_call = krait_cache_notifier;
+	cpufreq_register_notifier(&data->nb, CPUFREQ_TRANSITION_NOTIFIER);
+
+exit_vdd:
+	of_node_put(vdd);
+exit:
+	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