Subject: [RFC 5/9] PCI/pwrseq: add pwrseq core code

From: Bartosz Golaszewski <[email-masked]>
Date: Thu, 4 Jan 2024 14:01:19 +0100

From: Bartosz Golaszewski <[email-masked]>

Some PCIe devices must be powered-on before they can be detected on the
bus. Introduce a simple framework built around the PCIe port driver
which now instantiates its child devices from device-tree.

The way this works is: a DT node representing a PCIe 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 <[email-masked]>
---
 drivers/pci/pcie/Kconfig         |  2 +
 drivers/pci/pcie/Makefile        |  2 +
 drivers/pci/pcie/pwrseq/Kconfig  |  8 +++
 drivers/pci/pcie/pwrseq/Makefile |  3 ++
 drivers/pci/pcie/pwrseq/pwrseq.c | 83 ++++++++++++++++++++++++++++++++
 include/linux/pcie-pwrseq.h      | 24 +++++++++
 6 files changed, 122 insertions(+)
 create mode 100644 drivers/pci/pcie/pwrseq/Kconfig
 create mode 100644 drivers/pci/pcie/pwrseq/Makefile
 create mode 100644 drivers/pci/pcie/pwrseq/pwrseq.c
 create mode 100644 include/linux/pcie-pwrseq.h

diff --git a/drivers/pci/pcie/Kconfig b/drivers/pci/pcie/Kconfig
index 8999fcebde6a..064843ab6866 100644
--- a/drivers/pci/pcie/Kconfig
+++ b/drivers/pci/pcie/Kconfig
@@ -155,3 +155,5 @@ config PCIE_EDR
 	  the PCI Firmware Specification r3.2.  Enable this if you want to
 	  support hybrid DPC model which uses both firmware and OS to
 	  implement DPC.
+
+source "drivers/pci/pcie/pwrseq/Kconfig"
diff --git a/drivers/pci/pcie/Makefile b/drivers/pci/pcie/Makefile
index 8de4ed5f98f1..ace91384113d 100644
--- a/drivers/pci/pcie/Makefile
+++ b/drivers/pci/pcie/Makefile
@@ -13,3 +13,5 @@ obj-$(CONFIG_PCIE_PME)		+= pme.o
 obj-$(CONFIG_PCIE_DPC)		+= dpc.o
 obj-$(CONFIG_PCIE_PTM)		+= ptm.o
 obj-$(CONFIG_PCIE_EDR)		+= edr.o
+
+obj-$(CONFIG_PCIEPORTBUS)	+= pwrseq/
diff --git a/drivers/pci/pcie/pwrseq/Kconfig b/drivers/pci/pcie/pwrseq/Kconfig
new file mode 100644
index 000000000000..010e31f432c9
--- /dev/null
+++ b/drivers/pci/pcie/pwrseq/Kconfig
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0
+
+menuconfig PCIE_PWRSEQ
+	bool "PCIe Power Sequencing support"
+	depends on PCIEPORTBUS
+	help
+	  Say yes here to enable support for PCIe power sequencing
+	  drivers.
diff --git a/drivers/pci/pcie/pwrseq/Makefile b/drivers/pci/pcie/pwrseq/Makefile
new file mode 100644
index 000000000000..da99566594f6
--- /dev/null
+++ b/drivers/pci/pcie/pwrseq/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_PCIE_PWRSEQ)		+= pwrseq.o
diff --git a/drivers/pci/pcie/pwrseq/pwrseq.c b/drivers/pci/pcie/pwrseq/pwrseq.c
new file mode 100644
index 000000000000..c4f7958074c9
--- /dev/null
+++ b/drivers/pci/pcie/pwrseq/pwrseq.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2024 Linaro Ltd.
+ */
+
+#include <linux/cleanup.h>
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/pci.h>
+#include <linux/pcie-pwrseq.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+
+static int pcie_pwrseq_notify(struct notifier_block *nb, unsigned long action,
+			      void *data)
+{
+	struct pcie_pwrseq *pwrseq = container_of(nb, struct pcie_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 pcie_pwrseq_device_enable(struct pcie_pwrseq *pwrseq)
+{
+	if (!pwrseq->dev)
+		return -ENODEV;
+
+	pwrseq->nb.notifier_call = pcie_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(pcie_pwrseq_device_enable);
+
+void pcie_pwrseq_device_disable(struct pcie_pwrseq *pwrseq)
+{
+	bus_unregister_notifier(&pci_bus_type, &pwrseq->nb);
+}
+EXPORT_SYMBOL_GPL(pcie_pwrseq_device_disable);
+
+static void devm_pcie_pwrseq_device_disable(void *data)
+{
+	struct pcie_pwrseq *pwrseq = data;
+
+	pcie_pwrseq_device_disable(pwrseq);
+}
+
+int devm_pcie_pwrseq_device_enable(struct device *dev,
+				   struct pcie_pwrseq *pwrseq)
+{
+	int ret;
+
+	ret = pcie_pwrseq_device_enable(pwrseq);
+	if (ret)
+		return ret;
+
+	return devm_add_action_or_reset(dev, devm_pcie_pwrseq_device_disable,
+					pwrseq);
+}
+EXPORT_SYMBOL_GPL(devm_pcie_pwrseq_device_enable);
diff --git a/include/linux/pcie-pwrseq.h b/include/linux/pcie-pwrseq.h
new file mode 100644
index 000000000000..6abb5796754e
--- /dev/null
+++ b/include/linux/pcie-pwrseq.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2024 Linaro Ltd.
+ */
+
+#ifndef __PCIE_PWRSEQ_H__
+#define __PCIE_PWRSEQ_H__
+
+#include <linux/notifier.h>
+
+struct device;
+
+struct pcie_pwrseq {
+	struct notifier_block nb;
+	struct device *dev;
+	struct device_link *link;
+};
+
+int pcie_pwrseq_device_enable(struct pcie_pwrseq *pwrseq);
+void pcie_pwrseq_device_disable(struct pcie_pwrseq *pwrseq);
+int devm_pcie_pwrseq_device_enable(struct device *dev,
+				   struct pcie_pwrseq *pwrseq);
+
+#endif /* __PCIE_PWRSEQ_H__ */
-- 
2.40.1