sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 167 insertions, 0 deletions

diff --git a/drivers/clk/qcom/hfpll.c b/drivers/clk/qcom/hfpll.c
new file mode 100644
index 000000000..385964196
--- /dev/null
+++ b/drivers/clk/qcom/hfpll.c
@@ -0,0 +1,167 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018, The Linux Foundation. All rights reserved.
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/regmap.h>
+
+#include "clk-regmap.h"
+#include "clk-hfpll.h"
+
+static const struct hfpll_data qcs404 = {
+	.mode_reg = 0x00,
+	.l_reg = 0x04,
+	.m_reg = 0x08,
+	.n_reg = 0x0c,
+	.user_reg = 0x10,
+	.config_reg = 0x14,
+	.config_val = 0x430405d,
+	.status_reg = 0x1c,
+	.lock_bit = 16,
+
+	.user_val = 0x8,
+	.user_vco_mask = 0x100000,
+	.low_vco_max_rate = 1248000000,
+	.min_rate = 537600000UL,
+	.max_rate = 2900000000UL,
+};
+
+static const struct hfpll_data msm8976_a53 = {
+	.mode_reg = 0x00,
+	.l_reg = 0x04,
+	.m_reg = 0x08,
+	.n_reg = 0x0c,
+	.user_reg = 0x10,
+	.config_reg = 0x14,
+	.config_val = 0x341600,
+	.status_reg = 0x1c,
+	.lock_bit = 16,
+
+	.l_val = 0x35,
+	.user_val = 0x109,
+	.min_rate = 902400000UL,
+	.max_rate = 1478400000UL,
+};
+
+static const struct hfpll_data msm8976_a72 = {
+	.mode_reg = 0x00,
+	.l_reg = 0x04,
+	.m_reg = 0x08,
+	.n_reg = 0x0c,
+	.user_reg = 0x10,
+	.config_reg = 0x14,
+	.config_val = 0x4e0405d,
+	.status_reg = 0x1c,
+	.lock_bit = 16,
+
+	.l_val = 0x3e,
+	.user_val = 0x100109,
+	.min_rate = 940800000UL,
+	.max_rate = 2016000000UL,
+};
+
+static const struct hfpll_data msm8976_cci = {
+	.mode_reg = 0x00,
+	.l_reg = 0x04,
+	.m_reg = 0x08,
+	.n_reg = 0x0c,
+	.user_reg = 0x10,
+	.config_reg = 0x14,
+	.config_val = 0x141400,
+	.status_reg = 0x1c,
+	.lock_bit = 16,
+
+	.l_val = 0x20,
+	.user_val = 0x100109,
+	.min_rate = 556800000UL,
+	.max_rate = 902400000UL,
+};
+
+static const struct of_device_id qcom_hfpll_match_table[] = {
+	{ .compatible = "qcom,msm8976-hfpll-a53", .data = &msm8976_a53 },
+	{ .compatible = "qcom,msm8976-hfpll-a72", .data = &msm8976_a72 },
+	{ .compatible = "qcom,msm8976-hfpll-cci", .data = &msm8976_cci },
+	{ .compatible = "qcom,qcs404-hfpll", .data = &qcs404 },
+	/* Deprecated in bindings */
+	{ .compatible = "qcom,hfpll", .data = &qcs404 },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, qcom_hfpll_match_table);
+
+static const struct regmap_config hfpll_regmap_config = {
+	.reg_bits	= 32,
+	.reg_stride	= 4,
+	.val_bits	= 32,
+	.max_register	= 0x30,
+};
+
+static int qcom_hfpll_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	void __iomem *base;
+	struct regmap *regmap;
+	struct clk_hfpll *h;
+	struct clk_init_data init = {
+		.num_parents = 1,
+		.ops = &clk_ops_hfpll,
+		/*
+		 * rather than marking the clock critical and forcing the clock
+		 * to be always enabled, we make sure that the clock is not
+		 * disabled: the firmware remains responsible of enabling this
+		 * clock (for more info check the commit log)
+		 */
+		.flags = CLK_IGNORE_UNUSED,
+	};
+	int ret;
+	struct clk_parent_data pdata = { .index = 0 };
+
+	h = devm_kzalloc(dev, sizeof(*h), GFP_KERNEL);
+	if (!h)
+		return -ENOMEM;
+
+	base = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	regmap = devm_regmap_init_mmio(&pdev->dev, base, &hfpll_regmap_config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	if (of_property_read_string_index(dev->of_node, "clock-output-names",
+					  0, &init.name))
+		return -ENODEV;
+
+	init.parent_data = &pdata;
+
+	h->d = of_device_get_match_data(&pdev->dev);
+	h->clkr.hw.init = &init;
+	spin_lock_init(&h->lock);
+
+	ret = devm_clk_register_regmap(dev, &h->clkr);
+	if (ret) {
+		dev_err(dev, "failed to register regmap clock: %d\n", ret);
+		return ret;
+	}
+
+	return devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get,
+					   &h->clkr.hw);
+}
+
+static struct platform_driver qcom_hfpll_driver = {
+	.probe		= qcom_hfpll_probe,
+	.driver		= {
+		.name	= "qcom-hfpll",
+		.of_match_table = qcom_hfpll_match_table,
+	},
+};
+module_platform_driver(qcom_hfpll_driver);
+
+MODULE_DESCRIPTION("QCOM HFPLL Clock Driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:qcom-hfpll");