// SPDX-License-Identifier: GPL-2.0-only OR MIT
/*
 * Apple SART device driver
 * Copyright (C) The Asahi Linux Contributors
 *
 * Apple SART is a simple address filter for some DMA transactions.
 * Regions of physical memory must be added to the SART's allow
 * list before any DMA can target these. Unlike a proper
 * IOMMU no remapping can be done and special support in the
 * consumer driver is required since not all DMA transactions of
 * a single device are subject to SART filtering.
 */

#include <linux/soc/apple/sart.h>
#include <linux/atomic.h>
#include <linux/bits.h>
#include <linux/bitfield.h>
#include <linux/device.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
#include <linux/types.h>

#define APPLE_SART_MAX_ENTRIES 16

/* SARTv0 registers */
#define APPLE_SART0_CONFIG(idx)       (0x00 + 4 * (idx))
#define APPLE_SART0_CONFIG_FLAGS      GENMASK(28, 24)
#define APPLE_SART0_CONFIG_SIZE       GENMASK(18, 0)
#define APPLE_SART0_CONFIG_SIZE_SHIFT 12
#define APPLE_SART0_CONFIG_SIZE_MAX   GENMASK(18, 0)

#define APPLE_SART0_PADDR(idx)  (0x40 + 4 * (idx))
#define APPLE_SART0_PADDR_SHIFT 12

#define APPLE_SART0_FLAGS_ALLOW 0xf

/* SARTv2 registers */
#define APPLE_SART2_CONFIG(idx)       (0x00 + 4 * (idx))
#define APPLE_SART2_CONFIG_FLAGS      GENMASK(31, 24)
#define APPLE_SART2_CONFIG_SIZE       GENMASK(23, 0)
#define APPLE_SART2_CONFIG_SIZE_SHIFT 12
#define APPLE_SART2_CONFIG_SIZE_MAX   GENMASK(23, 0)

#define APPLE_SART2_PADDR(idx)  (0x40 + 4 * (idx))
#define APPLE_SART2_PADDR_SHIFT 12

#define APPLE_SART2_FLAGS_ALLOW 0xff

/* SARTv3 registers */
#define APPLE_SART3_CONFIG(idx) (0x00 + 4 * (idx))

#define APPLE_SART3_PADDR(idx)  (0x40 + 4 * (idx))
#define APPLE_SART3_PADDR_SHIFT 12

#define APPLE_SART3_SIZE(idx)  (0x80 + 4 * (idx))
#define APPLE_SART3_SIZE_SHIFT 12
#define APPLE_SART3_SIZE_MAX   GENMASK(29, 0)

#define APPLE_SART3_FLAGS_ALLOW 0xff

struct apple_sart_ops {
        void (*get_entry)(struct apple_sart *sart, int index, u8 *flags,
                          phys_addr_t *paddr, size_t *size);
        void (*set_entry)(struct apple_sart *sart, int index, u8 flags,
                          phys_addr_t paddr_shifted, size_t size_shifted);
        /* This is probably a bitfield but the exact meaning of each bit is unknown. */
        unsigned int flags_allow;
        unsigned int size_shift;
        unsigned int paddr_shift;
        size_t size_max;
};

struct apple_sart {
        struct device *dev;
        void __iomem *regs;

        const struct apple_sart_ops *ops;

        unsigned long protected_entries;
        unsigned long used_entries;
};

static void sart0_get_entry(struct apple_sart *sart, int index, u8 *flags,
        phys_addr_t *paddr, size_t *size)
{
        u32 cfg = readl(sart->regs + APPLE_SART0_CONFIG(index));
        phys_addr_t paddr_ = readl(sart->regs + APPLE_SART0_PADDR(index));
        size_t size_ = FIELD_GET(APPLE_SART0_CONFIG_SIZE, cfg);

        *flags = FIELD_GET(APPLE_SART0_CONFIG_FLAGS, cfg);
        *size = size_ << APPLE_SART0_CONFIG_SIZE_SHIFT;
        *paddr = paddr_ << APPLE_SART0_PADDR_SHIFT;
}

static void sart0_set_entry(struct apple_sart *sart, int index, u8 flags,
        phys_addr_t paddr_shifted, size_t size_shifted)
{
        u32 cfg;

        cfg = FIELD_PREP(APPLE_SART0_CONFIG_FLAGS, flags);
        cfg |= FIELD_PREP(APPLE_SART0_CONFIG_SIZE, size_shifted);

        writel(paddr_shifted, sart->regs + APPLE_SART0_PADDR(index));
        writel(cfg, sart->regs + APPLE_SART0_CONFIG(index));
}

static struct apple_sart_ops sart_ops_v0 = {
        .get_entry = sart0_get_entry,
        .set_entry = sart0_set_entry,
        .flags_allow = APPLE_SART0_FLAGS_ALLOW,
        .size_shift = APPLE_SART0_CONFIG_SIZE_SHIFT,
        .paddr_shift = APPLE_SART0_PADDR_SHIFT,
        .size_max = APPLE_SART0_CONFIG_SIZE_MAX,
};

static void sart2_get_entry(struct apple_sart *sart, int index, u8 *flags,
                            phys_addr_t *paddr, size_t *size)
{
        u32 cfg = readl(sart->regs + APPLE_SART2_CONFIG(index));
        phys_addr_t paddr_ = readl(sart->regs + APPLE_SART2_PADDR(index));
        size_t size_ = FIELD_GET(APPLE_SART2_CONFIG_SIZE, cfg);

        *flags = FIELD_GET(APPLE_SART2_CONFIG_FLAGS, cfg);
        *size = size_ << APPLE_SART2_CONFIG_SIZE_SHIFT;
        *paddr = paddr_ << APPLE_SART2_PADDR_SHIFT;
}

static void sart2_set_entry(struct apple_sart *sart, int index, u8 flags,
                            phys_addr_t paddr_shifted, size_t size_shifted)
{
        u32 cfg;

        cfg = FIELD_PREP(APPLE_SART2_CONFIG_FLAGS, flags);
        cfg |= FIELD_PREP(APPLE_SART2_CONFIG_SIZE, size_shifted);

        writel(paddr_shifted, sart->regs + APPLE_SART2_PADDR(index));
        writel(cfg, sart->regs + APPLE_SART2_CONFIG(index));
}

static struct apple_sart_ops sart_ops_v2 = {
        .get_entry = sart2_get_entry,
        .set_entry = sart2_set_entry,
        .flags_allow = APPLE_SART2_FLAGS_ALLOW,
        .size_shift = APPLE_SART2_CONFIG_SIZE_SHIFT,
        .paddr_shift = APPLE_SART2_PADDR_SHIFT,
        .size_max = APPLE_SART2_CONFIG_SIZE_MAX,
};

static void sart3_get_entry(struct apple_sart *sart, int index, u8 *flags,
                            phys_addr_t *paddr, size_t *size)
{
        phys_addr_t paddr_ = readl(sart->regs + APPLE_SART3_PADDR(index));
        size_t size_ = readl(sart->regs + APPLE_SART3_SIZE(index));

        *flags = readl(sart->regs + APPLE_SART3_CONFIG(index));
        *size = size_ << APPLE_SART3_SIZE_SHIFT;
        *paddr = paddr_ << APPLE_SART3_PADDR_SHIFT;
}

static void sart3_set_entry(struct apple_sart *sart, int index, u8 flags,
                            phys_addr_t paddr_shifted, size_t size_shifted)
{
        writel(paddr_shifted, sart->regs + APPLE_SART3_PADDR(index));
        writel(size_shifted, sart->regs + APPLE_SART3_SIZE(index));
        writel(flags, sart->regs + APPLE_SART3_CONFIG(index));
}

static struct apple_sart_ops sart_ops_v3 = {
        .get_entry = sart3_get_entry,
        .set_entry = sart3_set_entry,
        .flags_allow = APPLE_SART3_FLAGS_ALLOW,
        .size_shift = APPLE_SART3_SIZE_SHIFT,
        .paddr_shift = APPLE_SART3_PADDR_SHIFT,
        .size_max = APPLE_SART3_SIZE_MAX,
};

static int apple_sart_probe(struct platform_device *pdev)
{
        int i;
        struct apple_sart *sart;
        struct device *dev = &pdev->dev;

        sart = devm_kzalloc(dev, sizeof(*sart), GFP_KERNEL);
        if (!sart)
                return -ENOMEM;

        sart->dev = dev;
        sart->ops = of_device_get_match_data(dev);

        sart->regs = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(sart->regs))
                return PTR_ERR(sart->regs);

        for (i = 0; i < APPLE_SART_MAX_ENTRIES; ++i) {
                u8 flags;
                size_t size;
                phys_addr_t paddr;

                sart->ops->get_entry(sart, i, &flags, &paddr, &size);

                if (!flags)
                        continue;

                dev_dbg(sart->dev,
                        "SART bootloader entry: index %02d; flags: 0x%02x; paddr: %pa; size: 0x%zx\n",
                        i, flags, &paddr, size);
                set_bit(i, &sart->protected_entries);
        }

        platform_set_drvdata(pdev, sart);
        return 0;
}

struct apple_sart *devm_apple_sart_get(struct device *dev)
{
        struct device_node *sart_node;
        struct platform_device *sart_pdev;
        struct apple_sart *sart;

        sart_node = of_parse_phandle(dev->of_node, "apple,sart", 0);
        if (!sart_node)
                return ERR_PTR(-ENODEV);

        sart_pdev = of_find_device_by_node(sart_node);
        of_node_put(sart_node);

        if (!sart_pdev)
                return ERR_PTR(-ENODEV);

        sart = dev_get_drvdata(&sart_pdev->dev);
        if (!sart) {
                put_device(&sart_pdev->dev);
                return ERR_PTR(-EPROBE_DEFER);
        }

        device_link_add(dev, &sart_pdev->dev,
                        DL_FLAG_PM_RUNTIME | DL_FLAG_AUTOREMOVE_SUPPLIER);

        put_device(&sart_pdev->dev);

        return sart;
}
EXPORT_SYMBOL_GPL(devm_apple_sart_get);

static int sart_set_entry(struct apple_sart *sart, int index, u8 flags,
                          phys_addr_t paddr, size_t size)
{
        if (size & ((1 << sart->ops->size_shift) - 1))
                return -EINVAL;
        if (paddr & ((1 << sart->ops->paddr_shift) - 1))
                return -EINVAL;

        paddr >>= sart->ops->size_shift;
        size >>= sart->ops->paddr_shift;

        if (size > sart->ops->size_max)
                return -EINVAL;

        sart->ops->set_entry(sart, index, flags, paddr, size);
        return 0;
}

int apple_sart_add_allowed_region(struct apple_sart *sart, phys_addr_t paddr,
                                  size_t size)
{
        int i, ret;

        for (i = 0; i < APPLE_SART_MAX_ENTRIES; ++i) {
                if (test_bit(i, &sart->protected_entries))
                        continue;
                if (test_and_set_bit(i, &sart->used_entries))
                        continue;

                ret = sart_set_entry(sart, i, sart->ops->flags_allow, paddr,
                                     size);
                if (ret) {
                        dev_dbg(sart->dev,
                                "unable to set entry %d to [%pa, 0x%zx]\n",
                                i, &paddr, size);
                        clear_bit(i, &sart->used_entries);
                        return ret;
                }

                dev_dbg(sart->dev, "wrote [%pa, 0x%zx] to %d\n", &paddr, size,
                        i);
                return 0;
        }

        dev_warn(sart->dev,
                 "no free entries left to add [paddr: 0x%pa, size: 0x%zx]\n",
                 &paddr, size);

        return -EBUSY;
}
EXPORT_SYMBOL_GPL(apple_sart_add_allowed_region);

int apple_sart_remove_allowed_region(struct apple_sart *sart, phys_addr_t paddr,
                                     size_t size)
{
        int i;

        dev_dbg(sart->dev,
                "will remove [paddr: %pa, size: 0x%zx] from allowed regions\n",
                &paddr, size);

        for (i = 0; i < APPLE_SART_MAX_ENTRIES; ++i) {
                u8 eflags;
                size_t esize;
                phys_addr_t epaddr;

                if (test_bit(i, &sart->protected_entries))
                        continue;

                sart->ops->get_entry(sart, i, &eflags, &epaddr, &esize);

                if (epaddr != paddr || esize != size)
                        continue;

                sart->ops->set_entry(sart, i, 0, 0, 0);

                clear_bit(i, &sart->used_entries);
                dev_dbg(sart->dev, "cleared entry %d\n", i);
                return 0;
        }

        dev_warn(sart->dev, "entry [paddr: 0x%pa, size: 0x%zx] not found\n",
                 &paddr, size);

        return -EINVAL;
}
EXPORT_SYMBOL_GPL(apple_sart_remove_allowed_region);

static void apple_sart_shutdown(struct platform_device *pdev)
{
        struct apple_sart *sart = dev_get_drvdata(&pdev->dev);
        int i;

        for (i = 0; i < APPLE_SART_MAX_ENTRIES; ++i) {
                if (test_bit(i, &sart->protected_entries))
                        continue;

                sart->ops->set_entry(sart, i, 0, 0, 0);
        }
}

static const struct of_device_id apple_sart_of_match[] = {
        {
                .compatible = "apple,t6000-sart",
                .data = &sart_ops_v3,
        },
        {
                .compatible = "apple,t8103-sart",
                .data = &sart_ops_v2,
        },
        {
                .compatible = "apple,t8015-sart",
                .data = &sart_ops_v0,
        },
        {}
};
MODULE_DEVICE_TABLE(of, apple_sart_of_match);

static struct platform_driver apple_sart_driver = {
        .driver = {
                .name = "apple-sart",
                .of_match_table = apple_sart_of_match,
        },
        .probe = apple_sart_probe,
        .shutdown = apple_sart_shutdown,
};
module_platform_driver(apple_sart_driver);

MODULE_LICENSE("Dual MIT/GPL");
MODULE_AUTHOR("Sven Peter <sven@svenpeter.dev>");
MODULE_DESCRIPTION("Apple SART driver");