// SPDX-License-Identifier: GPL-2.0 /* Copyright (c) 2010, 2014 The Linux Foundation. All rights reserved. */ #include <linux/init.h> #include <asm/dcc.h> #include <asm/processor.h> #include "hvc_console.h" /* DCC Status Bits */ #define DCC_STATUS_RX (1 << 30) #define DCC_STATUS_TX (1 << 29) static int hvc_dcc_put_chars(uint32_t vt, const char *buf, int count) { int i; for (i = 0; i < count; i++) { while (__dcc_getstatus() & DCC_STATUS_TX) cpu_relax(); __dcc_putchar(buf[i]); } return count; } static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count) { int i; for (i = 0; i < count; ++i) if (__dcc_getstatus() & DCC_STATUS_RX) buf[i] = __dcc_getchar(); else break; return i; } static bool hvc_dcc_check(void) { unsigned long time = jiffies + (HZ / 10); /* Write a test character to check if it is handled */ __dcc_putchar('\n'); while (time_is_after_jiffies(time)) { if (!(__dcc_getstatus() & DCC_STATUS_TX)) return true; } return false; } static const struct hv_ops hvc_dcc_get_put_ops = { .get_chars = hvc_dcc_get_chars, .put_chars = hvc_dcc_put_chars, }; static int __init hvc_dcc_console_init(void) { int ret; if (!hvc_dcc_check()) return -ENODEV; /* Returns -1 if error */ ret = hvc_instantiate(0, 0, &hvc_dcc_get_put_ops); return ret < 0 ? -ENODEV : 0; } console_initcall(hvc_dcc_console_init); static int __init hvc_dcc_init(void) { struct hvc_struct *p; if (!hvc_dcc_check()) return -ENODEV; p = hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128); return PTR_ERR_OR_ZERO(p); } device_initcall(hvc_dcc_init);