misc: microchip: pci1xxxx: load auxiliary bus driver for the PIO function in the multi-function endpoint of pci1xxxx device.

pci1xxxx is a PCIe switch with a multi-function endpoint on one of its
downstream ports. PIO function is one of the functions in the
multi-function endpoint. PIO function combines a GPIO controller and also
an interface to program pci1xxxx's OTP & EEPROM. This auxiliary bus driver
is loaded for the PIO function and separate child devices are enumerated
for GPIO controller and OTP/EEPROM interface.

Signed-off-by: Kumaravel Thiagarajan <kumaravel.thiagarajan@microchip.com>
Link: https://lore.kernel.org/r/20220824200047.150308-2-kumaravel.thiagarajan@microchip.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

MAINTAINERS

@@ -13422,6 +13422,13 @@ S:	Supported
 F:	Documentation/devicetree/bindings/mtd/atmel-nand.txt
 F:	drivers/mtd/nand/raw/atmel/*
 
+MICROCHIP PCI1XXXX GP DRIVER
+M:	Kumaravel Thiagarajan <kumaravel.thiagarajan@microchip.com>
+L:	linux-gpio@vger.kernel.org
+S:	Supported
+F:	drivers/misc/mchp_pci1xxxx/mchp_pci1xxxx_gp.c
+F:	drivers/misc/mchp_pci1xxxx/mchp_pci1xxxx_gp.h
+
 MICROCHIP OTPC DRIVER
 M:	Claudiu Beznea <claudiu.beznea@microchip.com>
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)

drivers/misc/Kconfig

@@ -513,4 +513,5 @@ source "drivers/misc/cardreader/Kconfig"
 source "drivers/misc/habanalabs/Kconfig"
 source "drivers/misc/uacce/Kconfig"
 source "drivers/misc/pvpanic/Kconfig"
+source "drivers/misc/mchp_pci1xxxx/Kconfig"
 endmenu

drivers/misc/Makefile

@@ -60,4 +60,5 @@ obj-$(CONFIG_XILINX_SDFEC)	+= xilinx_sdfec.o
 obj-$(CONFIG_HISI_HIKEY_USB)	+= hisi_hikey_usb.o
 obj-$(CONFIG_HI6421V600_IRQ)	+= hi6421v600-irq.o
 obj-$(CONFIG_OPEN_DICE)		+= open-dice.o
-obj-$(CONFIG_VCPU_STALL_DETECTOR)	+= vcpu_stall_detector.o
+obj-$(CONFIG_GP_PCI1XXXX)	+= mchp_pci1xxxx/
+obj-$(CONFIG_VCPU_STALL_DETECTOR)	+= vcpu_stall_detector.o

drivers/misc/mchp_pci1xxxx/Kconfig

@@ -0,0 +1,11 @@
+config GP_PCI1XXXX
+       tristate "Microchip PCI1XXXX PCIe to GPIO Expander + OTP/EEPROM manager"
+       depends on PCI	
+       select GPIOLIB_IRQCHIP
+       help
+         PCI1XXXX is a PCIe GEN 3 switch with one of the endpoints having
+         multiple functions and one of the functions is a GPIO controller
+         which also has registers to interface with the OTP and EEPROM.
+         Select yes, no or module here to include or exclude the driver
+         for the GPIO function.
+

drivers/misc/mchp_pci1xxxx/Makefile

@@ -0,0 +1 @@
+obj-$(CONFIG_GP_PCI1XXXX) := mchp_pci1xxxx_gp.o

drivers/misc/mchp_pci1xxxx/mchp_pci1xxxx_gp.c

@@ -0,0 +1,166 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2022 Microchip Technology Inc.
+
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/spinlock.h>
+#include <linux/gpio/driver.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/idr.h>
+#include "mchp_pci1xxxx_gp.h"
+
+struct aux_bus_device {
+	struct auxiliary_device_wrapper *aux_device_wrapper[2];
+};
+
+static DEFINE_IDA(gp_client_ida);
+static const char aux_dev_otp_e2p_name[15] = "gp_otp_e2p";
+static const char aux_dev_gpio_name[15] = "gp_gpio";
+
+static void gp_auxiliary_device_release(struct device *dev)
+{
+	struct auxiliary_device_wrapper *aux_device_wrapper =
+		(struct auxiliary_device_wrapper *)container_of(dev,
+				struct auxiliary_device_wrapper, aux_dev.dev);
+
+	ida_free(&gp_client_ida, aux_device_wrapper->aux_dev.id);
+	kfree(aux_device_wrapper);
+}
+
+static int gp_aux_bus_probe(struct pci_dev *pdev, const struct pci_device_id *id)
+{
+	struct aux_bus_device *aux_bus;
+	int retval;
+
+	retval = pcim_enable_device(pdev);
+	if (retval)
+		return retval;
+
+	aux_bus = kzalloc(sizeof(*aux_bus), GFP_KERNEL);
+	if (!aux_bus)
+		return -ENOMEM;
+
+	aux_bus->aux_device_wrapper[0] = kzalloc(sizeof(*aux_bus->aux_device_wrapper[0]),
+						 GFP_KERNEL);
+	if (!aux_bus->aux_device_wrapper[0])
+		return -ENOMEM;
+
+	retval = ida_alloc(&gp_client_ida, GFP_KERNEL);
+	if (retval < 0)
+		goto err_ida_alloc_0;
+
+	aux_bus->aux_device_wrapper[0]->aux_dev.name = aux_dev_otp_e2p_name;
+	aux_bus->aux_device_wrapper[0]->aux_dev.dev.parent = &pdev->dev;
+	aux_bus->aux_device_wrapper[0]->aux_dev.dev.release = gp_auxiliary_device_release;
+	aux_bus->aux_device_wrapper[0]->aux_dev.id = retval;
+
+	aux_bus->aux_device_wrapper[0]->gp_aux_data.region_start = pci_resource_start(pdev, 0);
+	aux_bus->aux_device_wrapper[0]->gp_aux_data.region_length = pci_resource_end(pdev, 0);
+
+	retval = auxiliary_device_init(&aux_bus->aux_device_wrapper[0]->aux_dev);
+	if (retval < 0)
+		goto err_aux_dev_init_0;
+
+	retval = auxiliary_device_add(&aux_bus->aux_device_wrapper[0]->aux_dev);
+	if (retval)
+		goto err_aux_dev_add_0;
+
+	aux_bus->aux_device_wrapper[1] = kzalloc(sizeof(*aux_bus->aux_device_wrapper[1]),
+						 GFP_KERNEL);
+	if (!aux_bus->aux_device_wrapper[1])
+		return -ENOMEM;
+
+	retval = ida_alloc(&gp_client_ida, GFP_KERNEL);
+	if (retval < 0)
+		goto err_ida_alloc_1;
+
+	aux_bus->aux_device_wrapper[1]->aux_dev.name = aux_dev_gpio_name;
+	aux_bus->aux_device_wrapper[1]->aux_dev.dev.parent = &pdev->dev;
+	aux_bus->aux_device_wrapper[1]->aux_dev.dev.release = gp_auxiliary_device_release;
+	aux_bus->aux_device_wrapper[1]->aux_dev.id = retval;
+
+	aux_bus->aux_device_wrapper[1]->gp_aux_data.region_start = pci_resource_start(pdev, 0);
+	aux_bus->aux_device_wrapper[1]->gp_aux_data.region_length = pci_resource_end(pdev, 0);
+
+	retval = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_ALL_TYPES);
+
+	if (retval < 0)
+		return retval;
+
+	pdev->irq = pci_irq_vector(pdev, 0);
+	if (pdev->irq < 0)
+		return retval;
+
+	aux_bus->aux_device_wrapper[1]->gp_aux_data.irq_num = pdev->irq;
+
+	retval = auxiliary_device_init(&aux_bus->aux_device_wrapper[1]->aux_dev);
+	if (retval < 0)
+		goto err_aux_dev_init_1;
+
+	retval = auxiliary_device_add(&aux_bus->aux_device_wrapper[1]->aux_dev);
+	if (retval)
+		goto err_aux_dev_add_1;
+
+	pci_set_drvdata(pdev, aux_bus);
+	pci_set_master(pdev);
+
+	return 0;
+
+err_aux_dev_add_1:
+	auxiliary_device_uninit(&aux_bus->aux_device_wrapper[1]->aux_dev);
+
+err_aux_dev_init_1:
+	ida_free(&gp_client_ida, aux_bus->aux_device_wrapper[1]->aux_dev.id);
+
+err_ida_alloc_1:
+	kfree(aux_bus->aux_device_wrapper[1]);
+
+err_aux_dev_add_0:
+	auxiliary_device_uninit(&aux_bus->aux_device_wrapper[0]->aux_dev);
+
+err_aux_dev_init_0:
+	ida_free(&gp_client_ida, aux_bus->aux_device_wrapper[0]->aux_dev.id);
+
+err_ida_alloc_0:
+	kfree(aux_bus->aux_device_wrapper[0]);
+
+	return retval;
+}
+
+static void gp_aux_bus_remove(struct pci_dev *pdev)
+{
+	struct aux_bus_device *aux_bus = pci_get_drvdata(pdev);
+
+	auxiliary_device_delete(&aux_bus->aux_device_wrapper[0]->aux_dev);
+	auxiliary_device_uninit(&aux_bus->aux_device_wrapper[0]->aux_dev);
+	auxiliary_device_delete(&aux_bus->aux_device_wrapper[1]->aux_dev);
+	auxiliary_device_uninit(&aux_bus->aux_device_wrapper[1]->aux_dev);
+	kfree(aux_bus);
+	pci_disable_device(pdev);
+}
+
+static const struct pci_device_id pci1xxxx_tbl[] = {
+	{ PCI_DEVICE(0x1055, 0xA005) },
+	{ PCI_DEVICE(0x1055, 0xA015) },
+	{ PCI_DEVICE(0x1055, 0xA025) },
+	{ PCI_DEVICE(0x1055, 0xA035) },
+	{ PCI_DEVICE(0x1055, 0xA045) },
+	{ PCI_DEVICE(0x1055, 0xA055) },
+	{0,}
+};
+MODULE_DEVICE_TABLE(pci, pci1xxxx_tbl);
+
+static struct pci_driver pci1xxxx_gp_driver = {
+	.name = "PCI1xxxxGP",
+	.id_table = pci1xxxx_tbl,
+	.probe = gp_aux_bus_probe,
+	.remove = gp_aux_bus_remove,
+};
+
+module_pci_driver(pci1xxxx_gp_driver);
+
+MODULE_DESCRIPTION("Microchip Technology Inc. PCI1xxxx GP expander");
+MODULE_AUTHOR("Kumaravel Thiagarajan <kumaravel.thiagarajan@microchip.com>");
+MODULE_LICENSE("GPL");

drivers/misc/mchp_pci1xxxx/mchp_pci1xxxx_gp.h

@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2022 Microchip Technology Inc. */
+
+#ifndef _GPIO_PCI1XXXX_H
+#define _GPIO_PCI1XXXX_H
+
+#include <linux/spinlock.h>
+#include <linux/mutex.h>
+#include <linux/kthread.h>
+#include <linux/types.h>
+#include <linux/auxiliary_bus.h>
+
+/* Perform operations like variable length write, read and write with read back for OTP / EEPROM
+ * Perform bit mode write in OTP
+ */
+
+struct gp_aux_data_type {
+	int irq_num;
+	resource_size_t region_start;
+	resource_size_t region_length;
+};
+
+struct auxiliary_device_wrapper {
+	struct auxiliary_device aux_dev;
+	struct gp_aux_data_type gp_aux_data;
+};
+
+#endif