// SPDX-License-Identifier: GPL-2.0
/*
 * PCI Backend - Handles the virtual fields in the configuration space headers.
 *
 * Author: Ryan Wilson <hap9@epoch.ncsc.mil>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#define dev_fmt pr_fmt

#include <linux/kernel.h>
#include <linux/pci.h>
#include "pciback.h"
#include "conf_space.h"

struct pci_cmd_info {
	u16 val;
};

struct pci_bar_info {
	u32 val;
	u32 len_val;
	int which;
};

#define is_enable_cmd(value) ((value)&(PCI_COMMAND_MEMORY|PCI_COMMAND_IO))
#define is_master_cmd(value) ((value)&PCI_COMMAND_MASTER)

/* Bits guests are allowed to control in permissive mode. */
#define PCI_COMMAND_GUEST (PCI_COMMAND_MASTER|PCI_COMMAND_SPECIAL| \
			   PCI_COMMAND_INVALIDATE|PCI_COMMAND_VGA_PALETTE| \
			   PCI_COMMAND_WAIT|PCI_COMMAND_FAST_BACK)

static void *command_init(struct pci_dev *dev, int offset)
{
	struct pci_cmd_info *cmd = kmalloc(sizeof(*cmd), GFP_KERNEL);
	int err;

	if (!cmd)
		return ERR_PTR(-ENOMEM);

	err = pci_read_config_word(dev, PCI_COMMAND, &cmd->val);
	if (err) {
		kfree(cmd);
		return ERR_PTR(err);
	}

	return cmd;
}

static int command_read(struct pci_dev *dev, int offset, u16 *value, void *data)
{
	int ret = pci_read_config_word(dev, offset, value);
	const struct pci_cmd_info *cmd = data;

	*value &= PCI_COMMAND_GUEST;
	*value |= cmd->val & ~PCI_COMMAND_GUEST;

	return ret;
}

static int command_write(struct pci_dev *dev, int offset, u16 value, void *data)
{
	struct xen_pcibk_dev_data *dev_data;
	int err;
	u16 val;
	struct pci_cmd_info *cmd = data;

	dev_data = pci_get_drvdata(dev);
	if (!pci_is_enabled(dev) && is_enable_cmd(value)) {
		dev_dbg(&dev->dev, "enable\n");
		err = pci_enable_device(dev);
		if (err)
			return err;
		if (dev_data)
			dev_data->enable_intx = 1;
	} else if (pci_is_enabled(dev) && !is_enable_cmd(value)) {
		dev_dbg(&dev->dev, "disable\n");
		pci_disable_device(dev);
		if (dev_data)
			dev_data->enable_intx = 0;
	}

	if (!dev->is_busmaster && is_master_cmd(value)) {
		dev_dbg(&dev->dev, "set bus master\n");
		pci_set_master(dev);
	} else if (dev->is_busmaster && !is_master_cmd(value)) {
		dev_dbg(&dev->dev, "clear bus master\n");
		pci_clear_master(dev);
	}

	if (!(cmd->val & PCI_COMMAND_INVALIDATE) &&
	    (value & PCI_COMMAND_INVALIDATE)) {
		dev_dbg(&dev->dev, "enable memory-write-invalidate\n");
		err = pci_set_mwi(dev);
		if (err) {
			dev_warn(&dev->dev, "cannot enable memory-write-invalidate (%d)\n",
				err);
			value &= ~PCI_COMMAND_INVALIDATE;
		}
	} else if ((cmd->val & PCI_COMMAND_INVALIDATE) &&
		   !(value & PCI_COMMAND_INVALIDATE)) {
		dev_dbg(&dev->dev, "disable memory-write-invalidate\n");
		pci_clear_mwi(dev);
	}

	if (dev_data && dev_data->allow_interrupt_control &&
	    ((cmd->val ^ value) & PCI_COMMAND_INTX_DISABLE))
		pci_intx(dev, !(value & PCI_COMMAND_INTX_DISABLE));

	cmd->val = value;

	if (!xen_pcibk_permissive && (!dev_data || !dev_data->permissive))
		return 0;

	/* Only allow the guest to control certain bits. */
	err = pci_read_config_word(dev, offset, &val);
	if (err || val == value)
		return err;

	value &= PCI_COMMAND_GUEST;
	value |= val & ~PCI_COMMAND_GUEST;

	return pci_write_config_word(dev, offset, value);
}

static int rom_write(struct pci_dev *dev, int offset, u32 value, void *data)
{
	struct pci_bar_info *bar = data;

	if (unlikely(!bar)) {
		dev_warn(&dev->dev, "driver data not found\n");
		return XEN_PCI_ERR_op_failed;
	}

	/* A write to obtain the length must happen as a 32-bit write.
	 * This does not (yet) support writing individual bytes
	 */
	if ((value | ~PCI_ROM_ADDRESS_MASK) == ~0U)
		bar->which = 1;
	else {
		u32 tmpval;
		pci_read_config_dword(dev, offset, &tmpval);
		if (tmpval != bar->val && value == bar->val) {
			/* Allow restoration of bar value. */
			pci_write_config_dword(dev, offset, bar->val);
		}
		bar->which = 0;
	}

	/* Do we need to support enabling/disabling the rom address here? */

	return 0;
}

/* For the BARs, only allow writes which write ~0 or
 * the correct resource information
 * (Needed for when the driver probes the resource usage)
 */
static int bar_write(struct pci_dev *dev, int offset, u32 value, void *data)
{
	struct pci_bar_info *bar = data;
	unsigned int pos = (offset - PCI_BASE_ADDRESS_0) / 4;
	const struct resource *res = dev->resource;
	u32 mask;

	if (unlikely(!bar)) {
		dev_warn(&dev->dev, "driver data not found\n");
		return XEN_PCI_ERR_op_failed;
	}

	/* A write to obtain the length must happen as a 32-bit write.
	 * This does not (yet) support writing individual bytes
	 */
	if (res[pos].flags & IORESOURCE_IO)
		mask = ~PCI_BASE_ADDRESS_IO_MASK;
	else if (pos && (res[pos - 1].flags & IORESOURCE_MEM_64))
		mask = 0;
	else
		mask = ~PCI_BASE_ADDRESS_MEM_MASK;
	if ((value | mask) == ~0U)
		bar->which = 1;
	else {
		u32 tmpval;
		pci_read_config_dword(dev, offset, &tmpval);
		if (tmpval != bar->val && value == bar->val) {
			/* Allow restoration of bar value. */
			pci_write_config_dword(dev, offset, bar->val);
		}
		bar->which = 0;
	}

	return 0;
}

static int bar_read(struct pci_dev *dev, int offset, u32 * value, void *data)
{
	struct pci_bar_info *bar = data;

	if (unlikely(!bar)) {
		dev_warn(&dev->dev, "driver data not found\n");
		return XEN_PCI_ERR_op_failed;
	}

	*value = bar->which ? bar->len_val : bar->val;

	return 0;
}

static void *bar_init(struct pci_dev *dev, int offset)
{
	unsigned int pos;
	const struct resource *res = dev->resource;
	struct pci_bar_info *bar = kzalloc(sizeof(*bar), GFP_KERNEL);

	if (!bar)
		return ERR_PTR(-ENOMEM);

	if (offset == PCI_ROM_ADDRESS || offset == PCI_ROM_ADDRESS1)
		pos = PCI_ROM_RESOURCE;
	else {
		pos = (offset - PCI_BASE_ADDRESS_0) / 4;
		if (pos && (res[pos - 1].flags & IORESOURCE_MEM_64)) {
			/*
			 * Use ">> 16 >> 16" instead of direct ">> 32" shift
			 * to avoid warnings on 32-bit architectures.
			 */
			bar->val = res[pos - 1].start >> 16 >> 16;
			bar->len_val = -resource_size(&res[pos - 1]) >> 16 >> 16;
			return bar;
		}
	}

	if (!res[pos].flags ||
	    (res[pos].flags & (IORESOURCE_DISABLED | IORESOURCE_UNSET |
			       IORESOURCE_BUSY)))
		return bar;

	bar->val = res[pos].start |
		   (res[pos].flags & PCI_REGION_FLAG_MASK);
	bar->len_val = -resource_size(&res[pos]) |
		       (res[pos].flags & PCI_REGION_FLAG_MASK);

	return bar;
}

static void bar_reset(struct pci_dev *dev, int offset, void *data)
{
	struct pci_bar_info *bar = data;

	bar->which = 0;
}

static void bar_release(struct pci_dev *dev, int offset, void *data)
{
	kfree(data);
}

static int xen_pcibk_read_vendor(struct pci_dev *dev, int offset,
			       u16 *value, void *data)
{
	*value = dev->vendor;

	return 0;
}

static int xen_pcibk_read_device(struct pci_dev *dev, int offset,
			       u16 *value, void *data)
{
	*value = dev->device;

	return 0;
}

static int interrupt_read(struct pci_dev *dev, int offset, u8 * value,
			  void *data)
{
	*value = (u8) dev->irq;

	return 0;
}

static int bist_write(struct pci_dev *dev, int offset, u8 value, void *data)
{
	u8 cur_value;
	int err;

	err = pci_read_config_byte(dev, offset, &cur_value);
	if (err)
		goto out;

	if ((cur_value & ~PCI_BIST_START) == (value & ~PCI_BIST_START)
	    || value == PCI_BIST_START)
		err = pci_write_config_byte(dev, offset, value);

out:
	return err;
}

static const struct config_field header_common[] = {
	{
	 .offset    = PCI_VENDOR_ID,
	 .size      = 2,
	 .u.w.read  = xen_pcibk_read_vendor,
	},
	{
	 .offset    = PCI_DEVICE_ID,
	 .size      = 2,
	 .u.w.read  = xen_pcibk_read_device,
	},
	{
	 .offset    = PCI_COMMAND,
	 .size      = 2,
	 .init      = command_init,
	 .release   = bar_release,
	 .u.w.read  = command_read,
	 .u.w.write = command_write,
	},
	{
	 .offset    = PCI_INTERRUPT_LINE,
	 .size      = 1,
	 .u.b.read  = interrupt_read,
	},
	{
	 .offset    = PCI_INTERRUPT_PIN,
	 .size      = 1,
	 .u.b.read  = xen_pcibk_read_config_byte,
	},
	{
	 /* Any side effects of letting driver domain control cache line? */
	 .offset    = PCI_CACHE_LINE_SIZE,
	 .size      = 1,
	 .u.b.read  = xen_pcibk_read_config_byte,
	 .u.b.write = xen_pcibk_write_config_byte,
	},
	{
	 .offset    = PCI_LATENCY_TIMER,
	 .size      = 1,
	 .u.b.read  = xen_pcibk_read_config_byte,
	},
	{
	 .offset    = PCI_BIST,
	 .size      = 1,
	 .u.b.read  = xen_pcibk_read_config_byte,
	 .u.b.write = bist_write,
	},
	{}
};

#define CFG_FIELD_BAR(reg_offset)			\
	{						\
	.offset     = reg_offset,			\
	.size       = 4,				\
	.init       = bar_init,				\
	.reset      = bar_reset,			\
	.release    = bar_release,			\
	.u.dw.read  = bar_read,				\
	.u.dw.write = bar_write,			\
	}

#define CFG_FIELD_ROM(reg_offset)			\
	{						\
	.offset     = reg_offset,			\
	.size       = 4,				\
	.init       = bar_init,				\
	.reset      = bar_reset,			\
	.release    = bar_release,			\
	.u.dw.read  = bar_read,				\
	.u.dw.write = rom_write,			\
	}

static const struct config_field header_0[] = {
	CFG_FIELD_BAR(PCI_BASE_ADDRESS_0),
	CFG_FIELD_BAR(PCI_BASE_ADDRESS_1),
	CFG_FIELD_BAR(PCI_BASE_ADDRESS_2),
	CFG_FIELD_BAR(PCI_BASE_ADDRESS_3),
	CFG_FIELD_BAR(PCI_BASE_ADDRESS_4),
	CFG_FIELD_BAR(PCI_BASE_ADDRESS_5),
	CFG_FIELD_ROM(PCI_ROM_ADDRESS),
	{}
};

static const struct config_field header_1[] = {
	CFG_FIELD_BAR(PCI_BASE_ADDRESS_0),
	CFG_FIELD_BAR(PCI_BASE_ADDRESS_1),
	CFG_FIELD_ROM(PCI_ROM_ADDRESS1),
	{}
};

int xen_pcibk_config_header_add_fields(struct pci_dev *dev)
{
	int err;

	err = xen_pcibk_config_add_fields(dev, header_common);
	if (err)
		goto out;

	switch (dev->hdr_type) {
	case PCI_HEADER_TYPE_NORMAL:
		err = xen_pcibk_config_add_fields(dev, header_0);
		break;

	case PCI_HEADER_TYPE_BRIDGE:
		err = xen_pcibk_config_add_fields(dev, header_1);
		break;

	default:
		err = -EINVAL;
		dev_err(&dev->dev, "Unsupported header type %d!\n",
			dev->hdr_type);
		break;
	}

out:
	return err;
}