drivers/power/reset/syscon-reboot.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Generic Syscon Reboot Driver
   4  *
   5  * Copyright (c) 2013, Applied Micro Circuits Corporation
   6  * Author: Feng Kan <fkan@apm.com>
   7  */
   8 #include <linux/delay.h>
   9 #include <linux/io.h>
  10 #include <linux/notifier.h>
  11 #include <linux/mfd/syscon.h>
  12 #include <linux/of_address.h>
  13 #include <linux/of_device.h>
  14 #include <linux/platform_device.h>
  15 #include <linux/reboot.h>
  16 #include <linux/regmap.h>
  17
  18 struct syscon_reboot_context {
  19         struct regmap *map;
  20         u32 offset;
  21         u32 value;
  22         u32 mask;
  23         struct notifier_block restart_handler;
  24 };
  25
  26 static int syscon_restart_handle(struct notifier_block *this,
  27                                         unsigned long mode, void *cmd)
  28 {
  29         struct syscon_reboot_context *ctx =
  30                         container_of(this, struct syscon_reboot_context,
  31                                         restart_handler);
  32
  33         /* Issue the reboot */
  34         regmap_update_bits(ctx->map, ctx->offset, ctx->mask, ctx->value);
  35
  36         mdelay(1000);
  37
  38         pr_emerg("Unable to restart system\n");
  39         return NOTIFY_DONE;
  40 }
  41
  42 static int syscon_reboot_probe(struct platform_device *pdev)
  43 {
  44         struct syscon_reboot_context *ctx;
  45         struct device *dev = &pdev->dev;
  46         int mask_err, value_err;
  47         int err;
  48
  49         ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
  50         if (!ctx)
  51                 return -ENOMEM;
  52
  53         ctx->map = syscon_regmap_lookup_by_phandle(dev->of_node, "regmap");
  54         if (IS_ERR(ctx->map))
  55                 return PTR_ERR(ctx->map);
  56
  57         if (of_property_read_u32(pdev->dev.of_node, "offset", &ctx->offset))
  58                 return -EINVAL;
  59
  60         value_err = of_property_read_u32(pdev->dev.of_node, "value", &ctx->value);
  61         mask_err = of_property_read_u32(pdev->dev.of_node, "mask", &ctx->mask);
  62         if (value_err && mask_err) {
  63                 dev_err(dev, "unable to read 'value' and 'mask'");
  64                 return -EINVAL;
  65         }
  66
  67         if (value_err) {
  68                 /* support old binding */
  69                 ctx->value = ctx->mask;
  70                 ctx->mask = 0xFFFFFFFF;
  71         } else if (mask_err) {
  72                 /* support value without mask*/
  73                 ctx->mask = 0xFFFFFFFF;
  74         }
  75
  76         ctx->restart_handler.notifier_call = syscon_restart_handle;
  77         ctx->restart_handler.priority = 192;
  78         err = register_restart_handler(&ctx->restart_handler);
  79         if (err)
  80                 dev_err(dev, "can't register restart notifier (err=%d)\n", err);
  81
  82         return err;
  83 }
  84
  85 static const struct of_device_id syscon_reboot_of_match[] = {
  86         { .compatible = "syscon-reboot" },
  87         {}
  88 };
  89
  90 static struct platform_driver syscon_reboot_driver = {
  91         .probe = syscon_reboot_probe,
  92         .driver = {
  93                 .name = "syscon-reboot",
  94                 .of_match_table = syscon_reboot_of_match,
  95         },
  96 };
  97 builtin_platform_driver(syscon_reboot_driver);