text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   * PowerNV Real Time Clock.
   *
   * Copyright 2011 IBM Corp.
   */
  
  
  #include <linux/kernel.h>
  #include <linux/time.h>
  #include <linux/bcd.h>
  #include <linux/rtc.h>
  #include <linux/delay.h>
  #include <linux/platform_device.h>
  #include <linux/of_platform.h>
  
  #include <asm/opal.h>
  #include <asm/firmware.h>
  #include <asm/machdep.h>
  
  static void opal_to_tm(u32 y_m_d, u64 h_m_s_ms, struct rtc_time *tm)
  {
  	tm->tm_year	= ((bcd2bin(y_m_d >> 24) * 100) +
  			   bcd2bin((y_m_d >> 16) & 0xff)) - 1900;
  	tm->tm_mon	= bcd2bin((y_m_d >> 8) & 0xff) - 1;
  	tm->tm_mday	= bcd2bin(y_m_d & 0xff);
  	tm->tm_hour	= bcd2bin((h_m_s_ms >> 56) & 0xff);
  	tm->tm_min	= bcd2bin((h_m_s_ms >> 48) & 0xff);
  	tm->tm_sec	= bcd2bin((h_m_s_ms >> 40) & 0xff);
  	tm->tm_wday     = -1;
  }
  
  time64_t __init opal_get_boot_time(void)
  {
  	struct rtc_time tm;
  	u32 y_m_d;
  	u64 h_m_s_ms;
  	__be32 __y_m_d;
  	__be64 __h_m_s_ms;
  	long rc = OPAL_BUSY;
  
  	if (!opal_check_token(OPAL_RTC_READ))
  		return 0;
  
  	while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
  		rc = opal_rtc_read(&__y_m_d, &__h_m_s_ms);
  		if (rc == OPAL_BUSY_EVENT) {
  			mdelay(OPAL_BUSY_DELAY_MS);
  			opal_poll_events(NULL);
  		} else if (rc == OPAL_BUSY) {
  			mdelay(OPAL_BUSY_DELAY_MS);
  		}
  	}
  	if (rc != OPAL_SUCCESS)
  		return 0;
  
  	y_m_d = be32_to_cpu(__y_m_d);
  	h_m_s_ms = be64_to_cpu(__h_m_s_ms);
  	opal_to_tm(y_m_d, h_m_s_ms, &tm);
  	return rtc_tm_to_time64(&tm);
  }
  
  static __init int opal_time_init(void)
  {
  	struct platform_device *pdev;
  	struct device_node *rtc;
  
  	rtc = of_find_node_by_path("/ibm,opal/rtc");
  	if (rtc) {
  		pdev = of_platform_device_create(rtc, "opal-rtc", NULL);
  		of_node_put(rtc);
  	} else {
  		if (opal_check_token(OPAL_RTC_READ) ||
  		    opal_check_token(OPAL_READ_TPO))
  			pdev = platform_device_register_simple("opal-rtc", -1,
  							       NULL, 0);
  		else
  			return -ENODEV;
  	}
  
  	return PTR_ERR_OR_ZERO(pdev);
  }
  machine_subsys_initcall(powernv, opal_time_init);
  