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, 102 insertions, 0 deletions

diff --git a/sound/soc/sof/sof-acpi-dev.c b/sound/soc/sof/sof-acpi-dev.c
new file mode 100644
index 000000000..68bf1b570
--- /dev/null
+++ b/sound/soc/sof/sof-acpi-dev.c
@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
+//
+// This file is provided under a dual BSD/GPLv2 license.  When using or
+// redistributing this file, you may do so under either license.
+//
+// Copyright(c) 2018 Intel Corporation
+//
+// Author: Liam Girdwood <liam.r.girdwood@linux.intel.com>
+//
+
+#include <linux/acpi.h>
+#include <linux/firmware.h>
+#include <linux/module.h>
+#include <linux/pm_runtime.h>
+#include <sound/soc-acpi.h>
+#include <sound/soc-acpi-intel-match.h>
+#include <sound/sof.h>
+#include "../intel/common/soc-intel-quirks.h"
+#include "ops.h"
+#include "sof-acpi-dev.h"
+
+/* platform specific devices */
+#include "intel/shim.h"
+
+static char *fw_path;
+module_param(fw_path, charp, 0444);
+MODULE_PARM_DESC(fw_path, "deprecated - moved to snd-sof module.");
+
+static char *tplg_path;
+module_param(tplg_path, charp, 0444);
+MODULE_PARM_DESC(tplg_path, "deprecated - moved to snd-sof module.");
+
+static int sof_acpi_debug;
+module_param_named(sof_acpi_debug, sof_acpi_debug, int, 0444);
+MODULE_PARM_DESC(sof_acpi_debug, "SOF ACPI debug options (0x0 all off)");
+
+#define SOF_ACPI_DISABLE_PM_RUNTIME BIT(0)
+
+EXPORT_NS_DEV_PM_OPS(sof_acpi_pm, SND_SOC_SOF_ACPI_DEV) = {
+	SYSTEM_SLEEP_PM_OPS(snd_sof_suspend, snd_sof_resume)
+	RUNTIME_PM_OPS(snd_sof_runtime_suspend, snd_sof_runtime_resume,
+		       snd_sof_runtime_idle)
+};
+
+static void sof_acpi_probe_complete(struct device *dev)
+{
+	dev_dbg(dev, "Completing SOF ACPI probe");
+
+	if (sof_acpi_debug & SOF_ACPI_DISABLE_PM_RUNTIME)
+		return;
+
+	/* allow runtime_pm */
+	pm_runtime_set_autosuspend_delay(dev, SND_SOF_SUSPEND_DELAY_MS);
+	pm_runtime_use_autosuspend(dev);
+	pm_runtime_enable(dev);
+}
+
+int sof_acpi_probe(struct platform_device *pdev, const struct sof_dev_desc *desc)
+{
+	struct device *dev = &pdev->dev;
+	struct snd_sof_pdata *sof_pdata;
+
+	dev_dbg(dev, "ACPI DSP detected");
+
+	sof_pdata = devm_kzalloc(dev, sizeof(*sof_pdata), GFP_KERNEL);
+	if (!sof_pdata)
+		return -ENOMEM;
+
+	if (!desc->ops) {
+		dev_err(dev, "error: no matching ACPI descriptor ops\n");
+		return -ENODEV;
+	}
+
+	sof_pdata->desc = desc;
+	sof_pdata->dev = &pdev->dev;
+
+	sof_pdata->ipc_file_profile_base.ipc_type = desc->ipc_default;
+	sof_pdata->ipc_file_profile_base.fw_path = fw_path;
+	sof_pdata->ipc_file_profile_base.tplg_path = tplg_path;
+
+	/* set callback to be called on successful device probe to enable runtime_pm */
+	sof_pdata->sof_probe_complete = sof_acpi_probe_complete;
+
+	/* call sof helper for DSP hardware probe */
+	return snd_sof_device_probe(dev, sof_pdata);
+}
+EXPORT_SYMBOL_NS(sof_acpi_probe, "SND_SOC_SOF_ACPI_DEV");
+
+void sof_acpi_remove(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+
+	if (!(sof_acpi_debug & SOF_ACPI_DISABLE_PM_RUNTIME))
+		pm_runtime_disable(dev);
+
+	/* call sof helper for DSP hardware remove */
+	snd_sof_device_remove(dev);
+}
+EXPORT_SYMBOL_NS(sof_acpi_remove, "SND_SOC_SOF_ACPI_DEV");
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_DESCRIPTION("SOF support for ACPI platforms");