[PATCH 6/9] PCI/pwrseq: add pwrseq core code

[Bartosz Golaszewski <brgl@bgdev.pl>]

From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Some PCI devices must be powered-on before they can be detected on the
bus. Introduce a simple framework reusing the existing PCI OF
infrastructure.

The way this works is: a DT node representing a PCI device connected to
the port can be matched against its power sequencing platform driver. If
the match succeeds, the driver is responsible for powering-up the device
and calling pcie_pwrseq_device_enable() which will trigger a PCI bus
rescan as well as subscribe to PCI bus notifications.

When the device is detected and created, we'll make it consume the same
DT node that the platform device did. When the device is bound, we'll
create a device link between it and the parent power sequencing device.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/pci/Kconfig         |  1 +
 drivers/pci/Makefile        |  1 +
 drivers/pci/pwrseq/Kconfig  |  8 ++++
 drivers/pci/pwrseq/Makefile |  3 ++
 drivers/pci/pwrseq/pwrseq.c | 82 +++++++++++++++++++++++++++++++++++++
 include/linux/pci-pwrseq.h  | 24 +++++++++++
 6 files changed, 119 insertions(+)
 create mode 100644 drivers/pci/pwrseq/Kconfig
 create mode 100644 drivers/pci/pwrseq/Makefile
 create mode 100644 drivers/pci/pwrseq/pwrseq.c
 create mode 100644 include/linux/pci-pwrseq.h

diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 74147262625b..e0fd5caa1ffc 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -291,5 +291,6 @@ source "drivers/pci/hotplug/Kconfig"
 source "drivers/pci/controller/Kconfig"
 source "drivers/pci/endpoint/Kconfig"
 source "drivers/pci/switch/Kconfig"
+source "drivers/pci/pwrseq/Kconfig"
 
 endif
diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
index cc8b4e01e29d..0a1673ef2c9e 100644
--- a/drivers/pci/Makefile
+++ b/drivers/pci/Makefile
@@ -9,6 +9,7 @@ obj-$(CONFIG_PCI)		+= access.o bus.o probe.o host-bridge.o \
 
 obj-$(CONFIG_PCI)		+= msi/
 obj-$(CONFIG_PCI)		+= pcie/
+obj-$(CONFIG_PCI)		+= pwrseq/
 
 ifdef CONFIG_PCI
 obj-$(CONFIG_PROC_FS)		+= proc.o
diff --git a/drivers/pci/pwrseq/Kconfig b/drivers/pci/pwrseq/Kconfig
new file mode 100644
index 000000000000..a721a8a955c3
--- /dev/null
+++ b/drivers/pci/pwrseq/Kconfig
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0
+
+menu "PCI Power sequencing drivers"
+
+config PCI_PWRSEQ
+	bool
+
+endmenu
diff --git a/drivers/pci/pwrseq/Makefile b/drivers/pci/pwrseq/Makefile
new file mode 100644
index 000000000000..4052b6bb5aa5
--- /dev/null
+++ b/drivers/pci/pwrseq/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_PCI_PWRSEQ)		+= pwrseq.o
diff --git a/drivers/pci/pwrseq/pwrseq.c b/drivers/pci/pwrseq/pwrseq.c
new file mode 100644
index 000000000000..a750c7bc6830
--- /dev/null
+++ b/drivers/pci/pwrseq/pwrseq.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2024 Linaro Ltd.
+ */
+
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/pci.h>
+#include <linux/pci-pwrseq.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+
+static int pci_pwrseq_notify(struct notifier_block *nb, unsigned long action,
+			     void *data)
+{
+	struct pci_pwrseq *pwrseq = container_of(nb, struct pci_pwrseq, nb);
+	struct device *dev = data;
+
+	if (dev_fwnode(dev) != dev_fwnode(pwrseq->dev))
+		return NOTIFY_DONE;
+
+	switch (action) {
+	case BUS_NOTIFY_ADD_DEVICE:
+		device_set_of_node_from_dev(dev, pwrseq->dev);
+		break;
+	case BUS_NOTIFY_BOUND_DRIVER:
+		pwrseq->link = device_link_add(dev, pwrseq->dev,
+					       DL_FLAG_AUTOREMOVE_CONSUMER);
+		if (!pwrseq->link)
+			dev_err(pwrseq->dev, "Failed to add device link\n");
+		break;
+	case BUS_NOTIFY_UNBOUND_DRIVER:
+		device_link_del(pwrseq->link);
+		break;
+	}
+
+	return NOTIFY_DONE;
+}
+
+int pci_pwrseq_device_enable(struct pci_pwrseq *pwrseq)
+{
+	if (!pwrseq->dev)
+		return -ENODEV;
+
+	pwrseq->nb.notifier_call = pci_pwrseq_notify;
+	bus_register_notifier(&pci_bus_type, &pwrseq->nb);
+
+	pci_lock_rescan_remove();
+	pci_rescan_bus(to_pci_dev(pwrseq->dev->parent)->bus);
+	pci_unlock_rescan_remove();
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pci_pwrseq_device_enable);
+
+void pci_pwrseq_device_disable(struct pci_pwrseq *pwrseq)
+{
+	bus_unregister_notifier(&pci_bus_type, &pwrseq->nb);
+}
+EXPORT_SYMBOL_GPL(pci_pwrseq_device_disable);
+
+static void devm_pci_pwrseq_device_disable(void *data)
+{
+	struct pci_pwrseq *pwrseq = data;
+
+	pci_pwrseq_device_disable(pwrseq);
+}
+
+int devm_pci_pwrseq_device_enable(struct device *dev,
+				  struct pci_pwrseq *pwrseq)
+{
+	int ret;
+
+	ret = pci_pwrseq_device_enable(pwrseq);
+	if (ret)
+		return ret;
+
+	return devm_add_action_or_reset(dev, devm_pci_pwrseq_device_disable,
+					pwrseq);
+}
+EXPORT_SYMBOL_GPL(devm_pci_pwrseq_device_enable);
diff --git a/include/linux/pci-pwrseq.h b/include/linux/pci-pwrseq.h
new file mode 100644
index 000000000000..137b82b99d1c
--- /dev/null
+++ b/include/linux/pci-pwrseq.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2024 Linaro Ltd.
+ */
+
+#ifndef __PCI_PWRSEQ_H__
+#define __PCI_PWRSEQ_H__
+
+#include <linux/notifier.h>
+
+struct device;
+
+struct pci_pwrseq {
+	struct notifier_block nb;
+	struct device *dev;
+	struct device_link *link;
+};
+
+int pci_pwrseq_device_enable(struct pci_pwrseq *pwrseq);
+void pci_pwrseq_device_disable(struct pci_pwrseq *pwrseq);
+int devm_pci_pwrseq_device_enable(struct device *dev,
+				  struct pci_pwrseq *pwrseq);
+
+#endif /* __PCI_PWRSEQ_H__ */
-- 
2.40.1