[RFC PATCH 6/9] memory: apple: Add apple-mcc driver to manage MCC perf in Apple SoCs

[Hector Martin]

This driver binds to the memory controller hardware in Apple SoCs such
as the Apple M1, and provides a power domain that downstream devices can
use to change the performance state of the memory controller.

Signed-off-by: Hector Martin <marcan@xxxxxxxxx>
---
 drivers/memory/Kconfig     |   9 +++
 drivers/memory/Makefile    |   1 +
 drivers/memory/apple-mcc.c | 130 +++++++++++++++++++++++++++++++++++++
 3 files changed, 140 insertions(+)
 create mode 100644 drivers/memory/apple-mcc.c

diff --git a/drivers/memory/Kconfig b/drivers/memory/Kconfig
index 72c0df129d5c..48ef3d563a1c 100644
--- a/drivers/memory/Kconfig
+++ b/drivers/memory/Kconfig
@@ -30,6 +30,15 @@ config ARM_PL172_MPMC
 	  If you have an embedded system with an AMBA bus and a PL172
 	  controller, say Y or M here.
 
+config APPLE_MCC
+	tristate "Apple SoC MCC driver"
+	default y if ARCH_APPLE
+	select PM_GENERIC_DOMAINS
+	depends on ARCH_APPLE || COMPILE_TEST
+	help
+	  This driver manages performance tuning for the memory controller in
+	  Apple SoCs, such as the Apple M1.
+
 config ATMEL_SDRAMC
 	bool "Atmel (Multi-port DDR-)SDRAM Controller"
 	default y if ARCH_AT91
diff --git a/drivers/memory/Makefile b/drivers/memory/Makefile
index bc7663ed1c25..947840cbd2d4 100644
--- a/drivers/memory/Makefile
+++ b/drivers/memory/Makefile
@@ -8,6 +8,7 @@ ifeq ($(CONFIG_DDR),y)
 obj-$(CONFIG_OF)		+= of_memory.o
 endif
 obj-$(CONFIG_ARM_PL172_MPMC)	+= pl172.o
+obj-$(CONFIG_APPLE_MCC)		+= apple-mcc.o
 obj-$(CONFIG_ATMEL_SDRAMC)	+= atmel-sdramc.o
 obj-$(CONFIG_ATMEL_EBI)		+= atmel-ebi.o
 obj-$(CONFIG_BRCMSTB_DPFE)	+= brcmstb_dpfe.o
diff --git a/drivers/memory/apple-mcc.c b/drivers/memory/apple-mcc.c
new file mode 100644
index 000000000000..55959f034b9a
--- /dev/null
+++ b/drivers/memory/apple-mcc.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple SoC MCC memory controller performance control driver
+ *
+ * Copyright The Asahi Linux Contributors
+ */
+
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pm_domain.h>
+#include <linux/pm_opp.h>
+
+#define APPLE_MCC_PERF_CONFIG1  0xdc4
+#define APPLE_MCC_PERF_CONFIG2  0xdbc
+#define APPLE_MCC_CHANNEL(x)	((x) * 0x40000)
+
+struct apple_mcc {
+	struct device *dev;
+	struct generic_pm_domain genpd;
+	void __iomem *reg_base;
+	u32 num_channels;
+};
+
+#define to_apple_mcc(_genpd) container_of(_genpd, struct apple_mcc, genpd)
+
+static int apple_mcc_set_performance_state(struct generic_pm_domain *genpd, unsigned int state)
+{
+	struct apple_mcc *mcc = to_apple_mcc(genpd);
+	struct dev_pm_opp *opp;
+	struct device_node *np;
+	u32 perf_config[2];
+	unsigned int i;
+
+	dev_dbg(mcc->dev, "switching to perf state %d\n", state);
+
+	opp = dev_pm_opp_find_level_exact(&mcc->genpd.dev, state);
+	if (IS_ERR(opp))
+		return PTR_ERR(opp);
+
+	np = dev_pm_opp_get_of_node(opp);
+	if (of_property_read_u32_array(np, "apple,memory-perf-config",
+		perf_config, ARRAY_SIZE(perf_config))) {
+		dev_err(mcc->dev, "missing apple,memory-perf-config property");
+		of_node_put(np);
+		return -EINVAL;
+	}
+	of_node_put(np);
+
+	for (i = 0; i < mcc->num_channels; i++) {
+		writel_relaxed(perf_config[0],
+			       mcc->reg_base + APPLE_MCC_CHANNEL(i) + APPLE_MCC_PERF_CONFIG1);
+		writel_relaxed(perf_config[1],
+			       mcc->reg_base + APPLE_MCC_CHANNEL(i) + APPLE_MCC_PERF_CONFIG2);
+	}
+
+	return 0;
+}
+
+static unsigned int apple_mcc_opp_to_performance_state(struct generic_pm_domain *genpd,
+						       struct dev_pm_opp *opp)
+{
+	return dev_pm_opp_get_level(opp);
+}
+
+static int apple_mcc_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *node = dev->of_node;
+	struct apple_mcc *mcc;
+	int ret;
+
+	mcc = devm_kzalloc(dev, sizeof(*mcc), GFP_KERNEL);
+	if (!mcc)
+		return -ENOMEM;
+
+	mcc->reg_base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(mcc->reg_base))
+		return PTR_ERR(mcc->reg_base);
+
+	if (of_property_read_u32(node, "apple,num-channels", &mcc->num_channels)) {
+		dev_err(dev, "missing apple,num-channels property\n");
+		return -ENOENT;
+	}
+
+	mcc->dev = dev;
+	mcc->genpd.name = "apple-mcc-perf";
+	mcc->genpd.opp_to_performance_state = apple_mcc_opp_to_performance_state;
+	mcc->genpd.set_performance_state = apple_mcc_set_performance_state;
+
+	ret = pm_genpd_init(&mcc->genpd, NULL, false);
+	if (ret < 0) {
+		dev_err(dev, "pm_genpd_init failed\n");
+		return ret;
+	}
+
+	ret = of_genpd_add_provider_simple_noclk(node, &mcc->genpd);
+	if (ret < 0) {
+		dev_err(dev, "of_genpd_add_provider_simple failed\n");
+		return ret;
+	}
+
+	dev_info(dev, "Apple MCC performance driver initialized\n");
+
+	return 0;
+}
+
+static const struct of_device_id apple_mcc_of_match[] = {
+	{ .compatible = "apple,mcc" },
+	{}
+};
+
+MODULE_DEVICE_TABLE(of, apple_mcc_of_match);
+
+static struct platform_driver apple_mcc_driver = {
+	.probe = apple_mcc_probe,
+	.driver = {
+		.name = "apple-mcc",
+		.of_match_table = apple_mcc_of_match,
+	},
+};
+
+MODULE_AUTHOR("Hector Martin <marcan@xxxxxxxxx>");
+MODULE_DESCRIPTION("MCC memory controller performance tuning driver for Apple SoCs");
+MODULE_LICENSE("GPL v2");
+
+module_platform_driver(apple_mcc_driver);
-- 
2.33.0