PCI: hotplug: Add Ampere Altra Attention Indicator extension driver

On Ampere Altra, PCIe hotplug is handled through ACPI. A side interface is
also present to request system firmware control of the hotplug Attention
Indicators. Add an ACPI PCI Hotplug companion driver to support Attention
Indicator control.

Link: https://lore.kernel.org/r/20230930002036.6491-2-scott@os.amperecomputing.com
Signed-off-by: D Scott Phillips <scott@os.amperecomputing.com>
[bhelgaas: mask domain to low 4 bits]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: "Rafael J. Wysocki" <rafael@kernel.org>

drivers/pci/hotplug/Kconfig

@@ -61,6 +61,18 @@ config HOTPLUG_PCI_ACPI
 
 	  When in doubt, say N.
 
+config HOTPLUG_PCI_ACPI_AMPERE_ALTRA
+	tristate "ACPI PCI Hotplug driver Ampere Altra extensions"
+	depends on HOTPLUG_PCI_ACPI
+	depends on HAVE_ARM_SMCCC_DISCOVERY
+	help
+	  Say Y here if you have an Ampere Altra system.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called acpiphp_ampere_altra.
+
+	  When in doubt, say N.
+
 config HOTPLUG_PCI_ACPI_IBM
 	tristate "ACPI PCI Hotplug driver IBM extensions"
 	depends on HOTPLUG_PCI_ACPI

drivers/pci/hotplug/Makefile

@@ -23,6 +23,7 @@ obj-$(CONFIG_HOTPLUG_PCI_S390)		+= s390_pci_hpc.o
 
 # acpiphp_ibm extends acpiphp, so should be linked afterwards.
 
+obj-$(CONFIG_HOTPLUG_PCI_ACPI_AMPERE_ALTRA)	+= acpiphp_ampere_altra.o
 obj-$(CONFIG_HOTPLUG_PCI_ACPI_IBM)	+= acpiphp_ibm.o
 
 pci_hotplug-objs	:=	pci_hotplug_core.o

drivers/pci/hotplug/acpiphp_ampere_altra.c

@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ACPI PCI Hot Plug Extension for Ampere Altra. Allows control of
+ * attention LEDs via requests to system firmware.
+ *
+ * Copyright (C) 2023 Ampere Computing LLC
+ */
+
+#define pr_fmt(fmt) "acpiphp_ampere_altra: " fmt
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/pci_hotplug.h>
+#include <linux/platform_device.h>
+
+#include "acpiphp.h"
+
+#define HANDLE_OPEN	0xb0200000
+#define HANDLE_CLOSE	0xb0300000
+#define REQUEST		0xf0700000
+#define LED_CMD		0x00000004
+#define LED_ATTENTION	0x00000002
+#define LED_SET_ON	0x00000001
+#define LED_SET_OFF	0x00000002
+#define LED_SET_BLINK	0x00000003
+
+static u32 led_service_id[4];
+
+static int led_status(u8 status)
+{
+	switch (status) {
+	case 1: return LED_SET_ON;
+	case 2: return LED_SET_BLINK;
+	default: return LED_SET_OFF;
+	}
+}
+
+static int set_attention_status(struct hotplug_slot *slot, u8 status)
+{
+	struct arm_smccc_res res;
+	struct pci_bus *bus;
+	struct pci_dev *root_port;
+	unsigned long flags;
+	u32 handle;
+	int ret = 0;
+
+	bus = slot->pci_slot->bus;
+	root_port = pcie_find_root_port(bus->self);
+	if (!root_port)
+		return -ENODEV;
+
+	local_irq_save(flags);
+	arm_smccc_smc(HANDLE_OPEN, led_service_id[0], led_service_id[1],
+		      led_service_id[2], led_service_id[3], 0, 0, 0, &res);
+	if (res.a0) {
+		ret = -ENODEV;
+		goto out;
+	}
+	handle = res.a1 & 0xffff0000;
+
+	arm_smccc_smc(REQUEST, LED_CMD, led_status(status), LED_ATTENTION,
+		 (PCI_SLOT(root_port->devfn) << 4) | (pci_domain_nr(bus) & 0xf),
+		 0, 0, handle, &res);
+	if (res.a0)
+		ret = -ENODEV;
+
+	arm_smccc_smc(HANDLE_CLOSE, handle, 0, 0, 0, 0, 0, 0, &res);
+
+ out:
+	local_irq_restore(flags);
+	return ret;
+}
+
+static int get_attention_status(struct hotplug_slot *slot, u8 *status)
+{
+	return -EINVAL;
+}
+
+static struct acpiphp_attention_info ampere_altra_attn = {
+	.set_attn = set_attention_status,
+	.get_attn = get_attention_status,
+	.owner = THIS_MODULE,
+};
+
+static int altra_led_probe(struct platform_device *pdev)
+{
+	struct fwnode_handle *fwnode = dev_fwnode(&pdev->dev);
+	int ret;
+
+	ret = fwnode_property_read_u32_array(fwnode, "uuid", led_service_id, 4);
+	if (ret) {
+		dev_err(&pdev->dev, "can't find uuid\n");
+		return ret;
+	}
+
+	ret = acpiphp_register_attention(&ampere_altra_attn);
+	if (ret) {
+		dev_err(&pdev->dev, "can't register driver\n");
+		return ret;
+	}
+	return 0;
+}
+
+static void altra_led_remove(struct platform_device *pdev)
+{
+	acpiphp_unregister_attention(&ampere_altra_attn);
+}
+
+static const struct acpi_device_id altra_led_ids[] = {
+	{ "AMPC0008", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, altra_led_ids);
+
+static struct platform_driver altra_led_driver = {
+	.driver = {
+		.name = "ampere-altra-leds",
+		.acpi_match_table = altra_led_ids,
+	},
+	.probe = altra_led_probe,
+	.remove_new = altra_led_remove,
+};
+module_platform_driver(altra_led_driver);
+
+MODULE_AUTHOR("D Scott Phillips <scott@os.amperecomputing.com>");
+MODULE_LICENSE("GPL");