[PATCH v3 8/8] riscv_cbqri: Add CBQRI capacity allocation platform driver

[Drew Fustini]

Add a device-tree platform driver, bound to the generic
riscv,cbqri-capacity-controller compatible, that registers a CBQRI
capacity controller as the resctrl cache-allocation resource for the
cache it governs.

The driver follows the node's riscv,cbqri-cache phandle to that cache,
reads its level, and matches it against cacheinfo to get the resctrl
domain id and the harts sharing the cache. It then hands the controller
to riscv_cbqri_register_cc_dt() with the riscv,cbqri-rcid count from the
node.

Nothing is vendor-specific, and the DT "reg" is the CBQRI register block
itself, so any SoC that describes a CBQRI capacity controller in device
tree can reuse the driver unchanged.

Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Drew Fustini <fustini@xxxxxxxxxx>
---
 MAINTAINERS                      |   1 +
 drivers/resctrl/Kconfig          |  12 ++++
 drivers/resctrl/Makefile         |   1 +
 drivers/resctrl/cbqri_capacity.c | 132 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 146 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 64a95a4d795a..e0ffccd9ed6e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -23302,6 +23302,7 @@ F:	Documentation/devicetree/bindings/riscv/riscv,cbqri.yaml
 F:	arch/riscv/include/asm/qos.h
 F:	arch/riscv/include/asm/resctrl.h
 F:	arch/riscv/kernel/qos.c
+F:	drivers/resctrl/cbqri_capacity.c
 F:	drivers/resctrl/cbqri_devices.c
 F:	drivers/resctrl/cbqri_internal.h
 F:	drivers/resctrl/cbqri_resctrl.c
diff --git a/drivers/resctrl/Kconfig b/drivers/resctrl/Kconfig
index f8566c003d49..3645dd643117 100644
--- a/drivers/resctrl/Kconfig
+++ b/drivers/resctrl/Kconfig
@@ -41,6 +41,18 @@ menuconfig RISCV_CBQRI
 
 if RISCV_CBQRI
 
+config RISCV_CBQRI_CAPACITY
+	bool "RISC-V CBQRI cache capacity-allocation controller"
+	depends on OF
+	help
+	  Enable driver for a RISC-V CBQRI capacity controller that
+	  governs a CPU cache, matching the "riscv,cbqri-capacity-controller"
+	  compatible. The controller's cache phandle gives the cache level and the
+	  harts that share it, which the driver registers as a resctrl
+	  cache-allocation resource.
+
+	  Say N unless your device tree describes a CBQRI capacity controller.
+
 endif
 
 config RISCV_CBQRI_RESCTRL_FS
diff --git a/drivers/resctrl/Makefile b/drivers/resctrl/Makefile
index a7631712dba9..c8339113ef1f 100644
--- a/drivers/resctrl/Makefile
+++ b/drivers/resctrl/Makefile
@@ -7,3 +7,4 @@ ccflags-$(CONFIG_ARM64_MPAM_DRIVER_DEBUG)	+= -DDEBUG
 obj-$(CONFIG_RISCV_CBQRI)			+= cbqri.o
 cbqri-y						+= cbqri_devices.o
 cbqri-$(CONFIG_RISCV_CBQRI_RESCTRL_FS)		+= cbqri_resctrl.o
+cbqri-$(CONFIG_RISCV_CBQRI_CAPACITY)		+= cbqri_capacity.o
diff --git a/drivers/resctrl/cbqri_capacity.c b/drivers/resctrl/cbqri_capacity.c
new file mode 100644
index 000000000000..2172432eb328
--- /dev/null
+++ b/drivers/resctrl/cbqri_capacity.c
@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Platform driver for a RISC-V CBQRI capacity controller that backs a CPU
+ * cache. The controller is described in device tree by the generic
+ * "riscv,cbqri-capacity-controller" compatible together with a phandle to the
+ * cache node it governs. The driver hands it to the CBQRI core, which probes
+ * the capabilities register and exposes a controller that supports allocation
+ * as the resctrl cache allocation resource for that cache.
+ */
+
+#define pr_fmt(fmt) "cbqri-capacity: " fmt
+
+#include <linux/cacheinfo.h>
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/ioport.h>
+#include <linux/mod_devicetable.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/printk.h>
+#include <linux/riscv_cbqri.h>
+#include <linux/types.h>
+
+static int cbqri_capacity_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct cbqri_controller_info info = {};
+	struct device_node *cache_np;
+	cpumask_var_t cpu_mask;
+	struct resource *res;
+	u32 rcid_count, cache_level;
+	int cache_id, cpu, ret;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -EINVAL;
+
+	ret = of_property_read_u32(dev->of_node, "riscv,cbqri-rcid", &rcid_count);
+	if (ret) {
+		dev_err(dev, "missing riscv,cbqri-rcid\n");
+		return ret;
+	}
+
+	cache_np = of_parse_phandle(dev->of_node, "riscv,cbqri-cache", 0);
+	if (!cache_np) {
+		dev_err(dev, "missing riscv,cbqri-cache phandle\n");
+		return -EINVAL;
+	}
+
+	ret = of_property_read_u32(cache_np, "cache-level", &cache_level);
+	if (ret) {
+		dev_err(dev, "%pOF: missing cache-level\n", cache_np);
+		goto out_put;
+	}
+
+	if (!zalloc_cpumask_var(&cpu_mask, GFP_KERNEL)) {
+		ret = -ENOMEM;
+		goto out_put;
+	}
+
+	/*
+	 * Associate the controller with its cache instance via
+	 * cacheinfo. The matching cache provides the cache id and the
+	 * set of harts that share the cache.
+	 */
+	cache_id = -1;
+	cpus_read_lock();
+	for_each_online_cpu(cpu) {
+		struct cacheinfo *ci = get_cpu_cacheinfo_level(cpu, cache_level);
+
+		if (ci && ci->fw_token == cache_np) {
+			cache_id = ci->id;
+			cpumask_copy(cpu_mask, &ci->shared_cpu_map);
+			break;
+		}
+	}
+	cpus_read_unlock();
+
+	if (cache_id < 0) {
+		dev_err(dev, "%pOF: no online hart reports an L%u cache for this node\n",
+			cache_np, cache_level);
+		ret = -ENODEV;
+		goto out_free;
+	}
+
+	info.type = CBQRI_CONTROLLER_TYPE_CAPACITY;
+	info.addr = res->start;
+	info.size = resource_size(res);
+	info.rcid_count = rcid_count;
+	info.cache_id = cache_id;
+
+	ret = riscv_cbqri_register_cc_dt(&info, cache_level, cpu_mask);
+	if (ret) {
+		dev_err(dev, "failed to register capacity controller: %d\n", ret);
+		goto out_free;
+	}
+
+	dev_info(dev, "registered L%u capacity controller at %pa (cache_id=%d, rcid=%u)\n",
+		 cache_level, &info.addr, cache_id, rcid_count);
+
+out_free:
+	free_cpumask_var(cpu_mask);
+out_put:
+	of_node_put(cache_np);
+	return ret;
+}
+
+static const struct of_device_id cbqri_capacity_of_match[] = {
+	{ .compatible = "riscv,cbqri-capacity-controller" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, cbqri_capacity_of_match);
+
+static struct platform_driver cbqri_capacity_driver = {
+	.probe	= cbqri_capacity_probe,
+	.driver = {
+		.name		= "cbqri-capacity",
+		.of_match_table	= cbqri_capacity_of_match,
+		/*
+		 * The controller is registered permanently into the
+		 * CBQRI core for the life of the system. Block unbind
+		 * so userspace cannot leave a dangling controller.
+		 */
+		.suppress_bind_attrs = true,
+	},
+};
+
+/*
+ * Register at device_initcall so probe runs before the CBQRI core's
+ * late_initcall which walks the cbqri_controllers list.
+ */
+builtin_platform_driver(cbqri_capacity_driver);

-- 
2.43.0