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 */ 41 static 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 70 struct litex_soc_ctrl_device { 71 void __iomem *base; 72 struct notifier_block reset_nb; 73 }; 74 75 static 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 86 static const struct of_device_id litex_soc_ctrl_of_match[] = { 87 {.compatible = "litex,soc-controller"}, 88 {}, 89 }; 90 MODULE_DEVICE_TABLE(of, litex_soc_ctrl_of_match); 91 #endif /* CONFIG_OF */ 92 93 static 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 } 122 123 static 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 } 130 131 static 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 }; 139 140 module_platform_driver(litex_soc_ctrl_driver); 141 MODULE_DESCRIPTION("LiteX SoC Controller driver"); 142 MODULE_AUTHOR("Antmicro <www.antmicro.com>"); 143 MODULE_LICENSE("GPL v2"); 144