LXR linux/drivers/soc/litex/litex_soc

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * LiteX SoC Controller Driver
   4 *
   5 * Copyright (C) 2020 Antmicro <www.antmicro.com>
   6 *
   7 */
   8
   9#include <linux/litex.h>
  10#include <linux/device.h>
  11#include <linux/errno.h>
  12#include <linux/of.h>
  13#include <linux/platform_device.h>
  14#include <linux/printk.h>
  15#include <linux/module.h>
  16#include <linux/io.h>
  17#include <linux/reboot.h>
  18
  19/* reset register located at the base address */
  20#define RESET_REG_OFF           0x00
  21#define RESET_REG_VALUE         0x00000001
  22
  23#define SCRATCH_REG_OFF         0x04
  24#define SCRATCH_REG_VALUE       0x12345678
  25#define SCRATCH_TEST_VALUE      0xdeadbeef
  26
  27/*
  28 * Check LiteX CSR read/write access
  29 *
  30 * This function reads and writes a scratch register in order to verify if CSR
  31 * access works.
  32 *
  33 * In case any problems are detected, the driver should panic.
  34 *
  35 * Access to the LiteX CSR is, by design, done in CPU native endianness.
  36 * The driver should not dynamically configure access functions when
  37 * the endianness mismatch is detected. Such situation indicates problems in
  38 * the soft SoC design and should be solved at the LiteX generator level,
  39 * not in the software.
  40 */
  41static int litex_check_csr_access(void __iomem *reg_addr)
  42{
  43        unsigned long reg;
  44
  45        reg = litex_read32(reg_addr + SCRATCH_REG_OFF);
  46
  47        if (reg != SCRATCH_REG_VALUE) {
  48                panic("Scratch register read error - the system is probably broken! Expected: 0x%x but got: 0x%lx",
  49                        SCRATCH_REG_VALUE, reg);
  50                return -EINVAL;
  51        }
  52
  53        litex_write32(reg_addr + SCRATCH_REG_OFF, SCRATCH_TEST_VALUE);
  54        reg = litex_read32(reg_addr + SCRATCH_REG_OFF);
  55
  56        if (reg != SCRATCH_TEST_VALUE) {
  57                panic("Scratch register write error - the system is probably broken! Expected: 0x%x but got: 0x%lx",
  58                        SCRATCH_TEST_VALUE, reg);
  59                return -EINVAL;
  60        }
  61
  62        /* restore original value of the SCRATCH register */
  63        litex_write32(reg_addr + SCRATCH_REG_OFF, SCRATCH_REG_VALUE);
  64
  65        pr_info("LiteX SoC Controller driver initialized");
  66
  67        return 0;
  68}
  69
  70struct litex_soc_ctrl_device {
  71        void __iomem *base;
  72        struct notifier_block reset_nb;
  73};
  74
  75static int litex_reset_handler(struct notifier_block *this, unsigned long mode,
  76                               void *cmd)
  77{
  78        struct litex_soc_ctrl_device *soc_ctrl_dev =
  79                container_of(this, struct litex_soc_ctrl_device, reset_nb);
  80
  81        litex_write32(soc_ctrl_dev->base + RESET_REG_OFF, RESET_REG_VALUE);
  82        return NOTIFY_DONE;
  83}
  84
  85#ifdef CONFIG_OF
  86static const struct of_device_id litex_soc_ctrl_of_match[] = {
  87        {.compatible = "litex,soc-controller"},
  88        {},
  89};
  90MODULE_DEVICE_TABLE(of, litex_soc_ctrl_of_match);
  91#endif /* CONFIG_OF */
  92
  93static int litex_soc_ctrl_probe(struct platform_device *pdev)
  94{
  95        struct litex_soc_ctrl_device *soc_ctrl_dev;
  96        int error;
  97
  98        soc_ctrl_dev = devm_kzalloc(&pdev->dev, sizeof(*soc_ctrl_dev), GFP_KERNEL);
  99        if (!soc_ctrl_dev)
 100                return -ENOMEM;
 101
 102        soc_ctrl_dev->base = devm_platform_ioremap_resource(pdev, 0);
 103        if (IS_ERR(soc_ctrl_dev->base))
 104                return PTR_ERR(soc_ctrl_dev->base);
 105
 106        error = litex_check_csr_access(soc_ctrl_dev->base);
 107        if (error)
 108                return error;
 109
 110        platform_set_drvdata(pdev, soc_ctrl_dev);
 111
 112        soc_ctrl_dev->reset_nb.notifier_call = litex_reset_handler;
 113        soc_ctrl_dev->reset_nb.priority = 128;
 114        error = register_restart_handler(&soc_ctrl_dev->reset_nb);
 115        if (error) {
 116                dev_warn(&pdev->dev, "cannot register restart handler: %d\n",
 117                         error);
 118        }
 119
 120        return 0;
 121}
 122
 123static int litex_soc_ctrl_remove(struct platform_device *pdev)
 124{
 125        struct litex_soc_ctrl_device *soc_ctrl_dev = platform_get_drvdata(pdev);
 126
 127        unregister_restart_handler(&soc_ctrl_dev->reset_nb);
 128        return 0;
 129}
 130
 131static struct platform_driver litex_soc_ctrl_driver = {
 132        .driver = {
 133                .name = "litex-soc-controller",
 134                .of_match_table = of_match_ptr(litex_soc_ctrl_of_match)
 135        },
 136        .probe = litex_soc_ctrl_probe,
 137        .remove = litex_soc_ctrl_remove,
 138};
 139
 140module_platform_driver(litex_soc_ctrl_driver);
 141MODULE_DESCRIPTION("LiteX SoC Controller driver");
 142MODULE_AUTHOR("Antmicro <www.antmicro.com>");
 143MODULE_LICENSE("GPL v2");
 144