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

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

static LIST_HEAD(capabilities);
struct xen_pcibk_config_capability {
        struct list_head cap_list;

        int capability;

        /* If the device has the capability found above, add these fields */
        const struct config_field *fields;
};

static const struct config_field caplist_header[] = {
        {
         .offset    = PCI_CAP_LIST_ID,
         .size      = 2, /* encompass PCI_CAP_LIST_ID & PCI_CAP_LIST_NEXT */
         .u.w.read  = xen_pcibk_read_config_word,
         .u.w.write = NULL,
        },
        {}
};

static inline void register_capability(struct xen_pcibk_config_capability *cap)
{
        list_add_tail(&cap->cap_list, &capabilities);
}

int xen_pcibk_config_capability_add_fields(struct pci_dev *dev)
{
        int err = 0;
        struct xen_pcibk_config_capability *cap;
        int cap_offset;

        list_for_each_entry(cap, &capabilities, cap_list) {
                cap_offset = pci_find_capability(dev, cap->capability);
                if (cap_offset) {
                        dev_dbg(&dev->dev, "Found capability 0x%x at 0x%x\n",
                                cap->capability, cap_offset);

                        err = xen_pcibk_config_add_fields_offset(dev,
                                                               caplist_header,
                                                               cap_offset);
                        if (err)
                                goto out;
                        err = xen_pcibk_config_add_fields_offset(dev,
                                                               cap->fields,
                                                               cap_offset);
                        if (err)
                                goto out;
                }
        }

out:
        return err;
}

static int vpd_address_write(struct pci_dev *dev, int offset, u16 value,
                             void *data)
{
        /* Disallow writes to the vital product data */
        if (value & PCI_VPD_ADDR_F)
                return PCIBIOS_SET_FAILED;
        else
                return pci_write_config_word(dev, offset, value);
}

static const struct config_field caplist_vpd[] = {
        {
         .offset    = PCI_VPD_ADDR,
         .size      = 2,
         .u.w.read  = xen_pcibk_read_config_word,
         .u.w.write = vpd_address_write,
         },
        {
         .offset     = PCI_VPD_DATA,
         .size       = 4,
         .u.dw.read  = xen_pcibk_read_config_dword,
         .u.dw.write = NULL,
         },
        {}
};

static int pm_caps_read(struct pci_dev *dev, int offset, u16 *value,
                        void *data)
{
        int err;
        u16 real_value;

        err = pci_read_config_word(dev, offset, &real_value);
        if (err)
                goto out;

        *value = real_value & ~PCI_PM_CAP_PME_MASK;

out:
        return err;
}

/* PM_OK_BITS specifies the bits that the driver domain is allowed to change.
 * Can't allow driver domain to enable PMEs - they're shared */
#define PM_OK_BITS (PCI_PM_CTRL_PME_STATUS|PCI_PM_CTRL_DATA_SEL_MASK)

static int pm_ctrl_write(struct pci_dev *dev, int offset, u16 new_value,
                         void *data)
{
        int err;
        u16 old_value;
        pci_power_t new_state, old_state;

        err = pci_read_config_word(dev, offset, &old_value);
        if (err)
                goto out;

        old_state = (pci_power_t)(old_value & PCI_PM_CTRL_STATE_MASK);
        new_state = (pci_power_t)(new_value & PCI_PM_CTRL_STATE_MASK);

        new_value &= PM_OK_BITS;
        if ((old_value & PM_OK_BITS) != new_value) {
                new_value = (old_value & ~PM_OK_BITS) | new_value;
                err = pci_write_config_word(dev, offset, new_value);
                if (err)
                        goto out;
        }

        /* Let pci core handle the power management change */
        dev_dbg(&dev->dev, "set power state to %x\n", new_state);
        err = pci_set_power_state(dev, new_state);
        if (err) {
                err = PCIBIOS_SET_FAILED;
                goto out;
        }

 out:
        return err;
}

/* Ensure PMEs are disabled */
static void *pm_ctrl_init(struct pci_dev *dev, int offset)
{
        int err;
        u16 value;

        err = pci_read_config_word(dev, offset, &value);
        if (err)
                goto out;

        if (value & PCI_PM_CTRL_PME_ENABLE) {
                value &= ~PCI_PM_CTRL_PME_ENABLE;
                err = pci_write_config_word(dev, offset, value);
        }

out:
        return ERR_PTR(err);
}

static const struct config_field caplist_pm[] = {
        {
                .offset     = PCI_PM_PMC,
                .size       = 2,
                .u.w.read   = pm_caps_read,
        },
        {
                .offset     = PCI_PM_CTRL,
                .size       = 2,
                .init       = pm_ctrl_init,
                .u.w.read   = xen_pcibk_read_config_word,
                .u.w.write  = pm_ctrl_write,
        },
        {
                .offset     = PCI_PM_PPB_EXTENSIONS,
                .size       = 1,
                .u.b.read   = xen_pcibk_read_config_byte,
        },
        {
                .offset     = PCI_PM_DATA_REGISTER,
                .size       = 1,
                .u.b.read   = xen_pcibk_read_config_byte,
        },
        {}
};

static struct xen_pcibk_config_capability xen_pcibk_config_capability_pm = {
        .capability = PCI_CAP_ID_PM,
        .fields = caplist_pm,
};
static struct xen_pcibk_config_capability xen_pcibk_config_capability_vpd = {
        .capability = PCI_CAP_ID_VPD,
        .fields = caplist_vpd,
};

int xen_pcibk_config_capability_init(void)
{
        register_capability(&xen_pcibk_config_capability_vpd);
        register_capability(&xen_pcibk_config_capability_pm);

        return 0;
}