#include <linux/kernel.h>
#include <linux/errno.h>
#include "ktiva.h"
#include "ksync.h"
#include "kfile.h"
#include "krtc.h"

/////////////////////////////////////////////////////////////////////////////

#define _BCD2BIN(b)							((int)(((b) >> 4) * 10 + ((b) & 0x0F)))
#define _BIN2BCD(b)							((unsigned char)(((b) / 10) << 4 | ((b) % 10)))

#define _IS_12_HOUR_FORMAT_FLAG				(unsigned char)(1 << 6)
#define _IS_PM_FLAG							(unsigned char)(1 << 5)

#define _IS_12_HOUR_FORMAT(reg)				!!((reg) & _IS_12_HOUR_FORMAT_FLAG)
#define _IS_PM(reg)							!!((reg) & _IS_PM_FLAG)

#define _RTC_STOP_YIELD_DELAY				10
#define _RTC_STOP_MAX_YIELD_DELAY			1000

/////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////

static RTCTypes g_rtcType = RTCT_Unknown;

/////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////
// https://ww1.microchip.com/downloads/en/devicedoc/20005010f.pdf
// MCP7940

#define _I2C_SLV_ADDR_MCP7940				0x6f
#define _IS_MCP7940_OSC_RUN(reg)			(!!(reg & 0x20))	// OSCRUN:	1 = Oscillator is enabled and running
																// 			0 = Oscillator has stopped or has been disabled
#define _MCP7940_SRAM_ADDRESS				0x20
#define _MCP7940_SRAM_SIZE					64
#define _MCP7940_TEST_I2C_BUFFER_SIZE		28

/////////////////////////////////////////////////////////////////////////////

static int _MCP7940_get_date_time(struct file *pf, struct tm *ptm)
{
    int ret;
    unsigned char rtc[7];

	if(!(ret = TivaCmdGetI2C(pf, _I2C_SLV_ADDR_MCP7940, 0, sizeof(rtc), rtc, sizeof(rtc))))
	{
		if(_IS_MCP7940_OSC_RUN(rtc[3]))
		{
			memset(ptm, 0, sizeof(struct tm));

			ptm->tm_year	= _BCD2BIN(rtc[6]) + 100;
			ptm->tm_mon		= _BCD2BIN(rtc[5] & 0x1F) - 1;
			ptm->tm_mday	= _BCD2BIN(rtc[4] & 0x3F);
			if(_IS_12_HOUR_FORMAT(rtc[2]))	// 12h format
				ptm->tm_hour = _BCD2BIN(rtc[2] & 0x1F) + (_IS_PM(rtc[2]) ? 12 : 0);
			else	// 24h format (default)
				ptm->tm_hour = _BCD2BIN(rtc[2] & 0x3F);
			ptm->tm_min		= _BCD2BIN(rtc[1] & 0x7F);
			ptm->tm_sec		= _BCD2BIN(rtc[0] & 0x7F);
			ret = 0;
		}
		else
		{
			KALERT("%s: Oscillator not running!\n", __FUNCTION__);
			ret = -EIO;
		}
	}
	else
	{
		KALERT("%s: TivaCmdGetI2C failed (%d)\n", __FUNCTION__, ret);
		ret = -EIO;
	}
	
	return ret;
}

/////////////////////////////////////////////////////////////////////////////

static int _MCP7940_set_date_time(struct file *pf, const struct tm *ptm)
{
	bool bOscRun;
	unsigned int nMsSleep = 0;
    int ret, y, m;
    unsigned char rtc[9], reg = 0;

	/////////////////////////////////////////////////////////////////////////
	// Initiate a stop of the Oscillator by clearing register 0.

    if((ret = TivaCmdSetI2C(pf, _I2C_SLV_ADDR_MCP7940, 0, &reg, 1)))
    {
		KALERT("%s: TivaCmdSetI2C failed (%d)\n", __FUNCTION__, ret);
		return -EIO;
    }

	/////////////////////////////////////////////////////////////////////////
	// Meanwhile prepare the clock data that will be written to the RTC registers

	KALERT("Setting RTC to %04ld-%02d-%02dT%02d:%02d:%02d UTC\n", ptm->tm_year + 1900, ptm->tm_mon + 1, ptm->tm_mday, ptm->tm_hour, ptm->tm_min, ptm->tm_sec);

    y = ptm->tm_year - 100;
    m = ptm->tm_mon + 1;
    
    rtc[0] = _BIN2BCD(ptm->tm_sec) | 0x80;	// Write seconds and start Oscillator. This register will be written seperately at last!
    rtc[1] = _BIN2BCD(ptm->tm_min);
    rtc[2] = _BIN2BCD(ptm->tm_hour);		// uses 24h format
    rtc[3] = (ptm->tm_wday + 1) | 0x08;		// MCP7940 day of week is in range 1-7, struct tm is in range 0-6 (start with Sunday).
    										// Setting VBATEN (0x08) enables external battery backup supply.
    rtc[4] = _BIN2BCD(ptm->tm_mday);
    rtc[5] = _BIN2BCD(m);
    rtc[6] = _BIN2BCD(y);
    rtc[7] = 0x80;	// Set OUT bit in control register.
    rtc[8] = 0;		// Clear OSCTRIM explicitly. Disables  Digital Trimming.

	/////////////////////////////////////////////////////////////////////////
	// Wait for the oscillator to stop. This is indicated by OSCRUN = 0 in register 3.

    do
    {
		if((ret = TivaCmdGetI2C(pf, _I2C_SLV_ADDR_MCP7940, 3, 1, &reg, 1))) // read register 3
	    {
			KALERT("%s: TivaCmdGetI2C failed (%d)\n", __FUNCTION__, ret);
			return -EIO;
	    }
	    
	    if((bOscRun = _IS_MCP7940_OSC_RUN(reg)))		// if oscillator has not stopped yet
	    {
		    ksync_sleep_ms(_RTC_STOP_YIELD_DELAY);		// yield to another thread for _RTC_STOP_YIELD_DELAY ms
		    nMsSleep += _RTC_STOP_YIELD_DELAY;			// and sum up the delay to the total yield time.
		    
		    if(nMsSleep >= _RTC_STOP_MAX_YIELD_DELAY)	// if the total yield time has reached _RTC_STOP_MAX_YIELD_DELAY, return a timeout error.
		    {
				KALERT("%s: Timeout while trying to stop RTC Oscillator!\n", __FUNCTION__);
				return -ETIMEDOUT;
		    }
		}
    }
    while(bOscRun);

	/////////////////////////////////////////////////////////////////////////
	// write registers 1-8 (Minutes to Year and control/status and trim registers)

    if((ret = TivaCmdSetI2C(pf, _I2C_SLV_ADDR_MCP7940, 1, &rtc[1], sizeof(rtc) - 1)))
    {
		KALERT("%s: TivaCmdSetI2C failed (%d)\n", __FUNCTION__, ret);
		return -EIO;
    }

	/////////////////////////////////////////////////////////////////////////
	// write register 0 (Seconds and Start oscillator)

    if((ret = TivaCmdSetI2C(pf, _I2C_SLV_ADDR_MCP7940, 0, rtc, 1)))
    {
		KALERT("%s: TivaCmdSetI2C failed (%d)\n", __FUNCTION__, ret);
		return -EIO;
    }

	return 0;	// RTC should now be set and running
}

/////////////////////////////////////////////////////////////////////////////

static int _MCP7940_test_i2c(struct file *pf)
{
	size_t i;
    int ret;
    unsigned char write[_MCP7940_TEST_I2C_BUFFER_SIZE], read[_MCP7940_TEST_I2C_BUFFER_SIZE];

    for(i = 0; i < sizeof(write); ++i)
    {
    	write[i] = i;
    	read[i] = 0xFF;
    }

    if((ret = TivaCmdSetI2C(pf, _I2C_SLV_ADDR_MCP7940, _MCP7940_SRAM_ADDRESS, write, sizeof(write))))
    {
		KALERT("%s: TivaCmdSetI2C failed (%d)\n", __FUNCTION__, ret);
		return -EIO;
    }

    if((ret = TivaCmdGetI2C(pf, _I2C_SLV_ADDR_MCP7940, _MCP7940_SRAM_ADDRESS, sizeof(read), read, sizeof(read))))
    {
		KALERT("%s: TivaCmdGetI2C failed (%d)\n", __FUNCTION__, ret);
		return -EIO;
    }

	if((ret = memcmp(write, read, sizeof(read))))
	{
		KALERT("%s: R/W Data mismatch!\n", __FUNCTION__);
		ret = -EPROTO;
	}

    return ret;
}

/////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////
// https://datasheets.maximintegrated.com/en/ds/DS3231-DS3231S.pdf
// DS3231

#define _I2C_SLV_ADDR_DS3231				0x68
#define _IS_DS3231_OSC_RUN(reg)				(!(reg & 0x80))	// OSF (Oscillator Stop Flag):
															// 1 indicates that the oscillator either is stopped or was stopped for some period

/////////////////////////////////////////////////////////////////////////////

static int _DS3231_get_date_time(struct file *pf, struct tm *ptm)
{
    int ret;
    unsigned char rtc[16];

	if(!(ret = TivaCmdGetI2C(pf, _I2C_SLV_ADDR_DS3231, 0, sizeof(rtc), rtc, sizeof(rtc))))
	{
		if(_IS_DS3231_OSC_RUN(rtc[15]))
		{
			memset(ptm, 0, sizeof(struct tm));

			ptm->tm_year	= _BCD2BIN(rtc[6]) + 100;
			ptm->tm_mon		= _BCD2BIN(rtc[5] & 0x1F) - 1;
			ptm->tm_mday	= _BCD2BIN(rtc[4] & 0x3F);
			if(_IS_12_HOUR_FORMAT(rtc[2]))	// 12h format
				ptm->tm_hour = _BCD2BIN(rtc[2] & 0x1F) + (_IS_PM(rtc[2]) ? 12 : 0);
			else	// 24h format (default)
				ptm->tm_hour = _BCD2BIN(rtc[2] & 0x3F);
			ptm->tm_min		= _BCD2BIN(rtc[1] & 0x7F);
			ptm->tm_sec		= _BCD2BIN(rtc[0] & 0x7F);
			ret = 0;
		}
		else
		{
			KALERT("%s: Oscillator not running!\n", __FUNCTION__);
			ret = -EIO;
		}
	}
	else
	{
		KALERT("%s: TivaCmdGetI2C failed (%d)\n", __FUNCTION__, ret);
		ret = -EIO;
	}
	
	return ret;
}

/////////////////////////////////////////////////////////////////////////////

static int _DS3231_set_date_time(struct file *pf, const struct tm *ptm)
{
    int ret, y, m;
    unsigned char rtc[7], reg = 0;

	/////////////////////////////////////////////////////////////////////////
	// Prepare the clock data to be written to the RTC registers

	KALERT("Setting RTC to %04ld-%02d-%02dT%02d:%02d:%02d UTC\n", ptm->tm_year + 1900, ptm->tm_mon + 1, ptm->tm_mday, ptm->tm_hour, ptm->tm_min, ptm->tm_sec);

    y = ptm->tm_year - 100;
    m = ptm->tm_mon + 1;
    
    rtc[0] = _BIN2BCD(ptm->tm_sec);		// seconds
    rtc[1] = _BIN2BCD(ptm->tm_min);		// minutes
    rtc[2] = _BIN2BCD(ptm->tm_hour);	// hour, uses 24h format
    rtc[3] = (ptm->tm_wday + 1);		// DS3231 day of week is in range 1-7, struct tm is in range 0-6 (start with Sunday).
    rtc[4] = _BIN2BCD(ptm->tm_mday);	// day
    rtc[5] = _BIN2BCD(m);				// month
    rtc[6] = _BIN2BCD(y);				// year

	/////////////////////////////////////////////////////////////////////////
	// write registers 0-6 (Seconds to Year)
	// The countdown chain is reset whenever the seconds register is written (0h).  Once the countdown chain is
	// reset, to avoid rollover issues the remaining time and date registers must be written within 1 second.

    if((ret = TivaCmdSetI2C(pf, _I2C_SLV_ADDR_DS3231, 0, rtc, sizeof(rtc))))
    {
		KALERT("%s: TivaCmdSetI2C failed (%d)\n", __FUNCTION__, ret);
		return -EIO;
    }

	/////////////////////////////////////////////////////////////////////////
	// read/write register 15 (Status Register), to clear the OSF flag.

	if(!(ret = TivaCmdGetI2C(pf, _I2C_SLV_ADDR_DS3231, 15, 1, &reg, 1))) // read register 15
    {
    	reg &= 0x7F;	// clear OSF bit.

	    if((ret = TivaCmdSetI2C(pf, _I2C_SLV_ADDR_DS3231, 15, &reg, 1))) // write register 15
	    {
			KALERT("%s: TivaCmdSetI2C failed (%d)\n", __FUNCTION__, ret);
			return -EIO;
	    }
	}
	else
    {
		KALERT("%s: TivaCmdGetI2C failed (%d)\n", __FUNCTION__, ret);
		return -EIO;
    }

	return 0;	// RTC should now be set and running
}

/////////////////////////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////

int krtc_init(void)
{
    int i, ret = 0;
	struct file *pfSpiDev = NULL;
	g_rtcType = RTCT_Unknown;

	if((pfSpiDev = kf_open_locked(_SPI_DEVICE, O_RDWR, 0)))
	{
		if(KSpiInit(pfSpiDev))
		{
		    unsigned char rtc[7];

			if(!(ret = TivaCmdGetI2C(pfSpiDev, _I2C_SLV_ADDR_MCP7940, 0, sizeof(rtc), rtc, sizeof(rtc)))) // MCP7940
			{
				for(i = 0; i < 7; ++i)
				{
					if(rtc[i] != 0xFF)
					{
						g_rtcType = RTCT_MCP7940;
						break;
					}
				}
				
				if(g_rtcType == RTCT_Unknown)
				{
					if(!(ret = TivaCmdGetI2C(pfSpiDev, _I2C_SLV_ADDR_DS3231, 0, sizeof(rtc), rtc, sizeof(rtc)))) // DS3231
					{
						for(i = 0; i < 7; ++i)
						{
							if(rtc[i] != 0xFF)
							{
								g_rtcType = RTCT_DS3231;
								break;
							}
						}
					}
					else
					{
						KALERT("%s: TivaCmdGetI2C failed (%d)\n", __FUNCTION__, ret);
						ret = -EIO;
					}
				}
			}
			else
			{
				KALERT("%s: TivaCmdGetI2C failed (%d)\n", __FUNCTION__, ret);
				ret = -EIO;
			}
		}
		else
		{
			KALERT("%s: KSpiInit failed\n", __FUNCTION__);
			ret = -EIO;
		}

		kf_close(pfSpiDev);
	}
	else
	{
		KALERT("%s: kf_open_locked failed\n", __FUNCTION__);
		ret = -EIO;
	}

	if(g_rtcType == RTCT_Unknown)
	{
		KALERT("%s: Unable to determine RTC-Type!\n", __FUNCTION__);
		ret = -ENODEV;
	}

	return ret;
}

/////////////////////////////////////////////////////////////////////////////

RTCTypes krtc_get_type(void)
{
	return g_rtcType;
}

/////////////////////////////////////////////////////////////////////////////

int krtc_get_date_time(struct tm *ptm)
{
    int ret;
	struct file *pfSpiDev = NULL;
    
    if(!KRTC_IS_VALID_RTC_TYPE(g_rtcType))
    {
		KALERT("%s: Invalid RTC-Type!\n", __FUNCTION__);
		return -ENODEV;
    }

	if((pfSpiDev = kf_open_locked(_SPI_DEVICE, O_RDWR, 0)))
	{
		if(KSpiInit(pfSpiDev))
		{
			switch(g_rtcType)
			{
			case RTCT_MCP7940:
				if((ret = _MCP7940_get_date_time(pfSpiDev, ptm)))
					KALERT("%s: _MCP7940_get_date_time failed!\n", __FUNCTION__);
				break;
			case RTCT_DS3231:
				if((ret = _DS3231_get_date_time(pfSpiDev, ptm)))
					KALERT("%s: _DS3231_get_date_time failed!\n", __FUNCTION__);
				break;
			default:
				break;
			}
		}
		else
		{
			KALERT("%s: KSpiInit failed\n", __FUNCTION__);
			ret = -EIO;
		}

		kf_close(pfSpiDev);
	}
	else
	{
		KALERT("%s: kf_open_locked failed\n", __FUNCTION__);
		ret = -ENODEV;
	}

	return ret;
}

/////////////////////////////////////////////////////////////////////////////

int krtc_set_date_time(const struct tm *ptm)
{
    int ret;
	struct file *pfSpiDev = NULL;
//	unsigned long jStart = jiffies, jDiff;
    
    if(!KRTC_IS_VALID_RTC_TYPE(g_rtcType))
    {
		KALERT("%s: Invalid RTC-Type!\n", __FUNCTION__);
		return -ENODEV;
    }

	if((pfSpiDev = kf_open_locked(_SPI_DEVICE, O_RDWR, 0)))
	{
		if(KSpiInit(pfSpiDev))
		{
			switch(g_rtcType)
			{
			case RTCT_MCP7940:
//				jDiff = jiffies - jStart;
//				KALERT("%s: prep _MCP7940_set_date_time took %u us.\n", __FUNCTION__, jiffies_to_usecs(jDiff));
//				jStart = jiffies;
				if((ret = _MCP7940_set_date_time(pfSpiDev, ptm)))
					KALERT("%s: _MCP7940_set_date_time failed!\n", __FUNCTION__);
//				jDiff = jiffies - jStart;
//				KALERT("%s: call _MCP7940_set_date_time took %u us.\n", __FUNCTION__, jiffies_to_usecs(jDiff));
				break;
			case RTCT_DS3231:
				if((ret = _DS3231_set_date_time(pfSpiDev, ptm)))
					KALERT("%s: _DS3231_set_date_time failed!\n", __FUNCTION__);
				break;
			default:
				break;
			}
		}
		else
		{
			KALERT("%s: KSpiInit failed\n", __FUNCTION__);
			ret = -EIO;
		}

		kf_close(pfSpiDev);
	}
	else
	{
		KALERT("%s: kf_open_locked failed\n", __FUNCTION__);
		ret = -ENODEV;
	}

	return ret;
}

/////////////////////////////////////////////////////////////////////////////

int krtc_test_i2c(void)
{
    int ret;
	struct file *pfSpiDev = NULL;
    
    if(g_rtcType != RTCT_MCP7940)
    {
    	if(g_rtcType == RTCT_DS3231)
    	{
			KALERT("%s: I2C-Test not implemented in DS3231!\n", __FUNCTION__);
			return -ENOTSUPP;
    	}
    	else
    	{
			KALERT("%s: Invalid RTC-Type!\n", __FUNCTION__);
			return -ENODEV;
    	}
    }

	if((pfSpiDev = kf_open_locked(_SPI_DEVICE, O_RDWR, 0)))
	{
		if(KSpiInit(pfSpiDev))
		{
			if((ret = _MCP7940_test_i2c(pfSpiDev)))
				KALERT("%s: _MCP7940_test_i2c failed!\n", __FUNCTION__);
		}
		else
		{
			KALERT("%s: KSpiInit failed\n", __FUNCTION__);
			ret = -EIO;
		}

		kf_close(pfSpiDev);
	}
	else
	{
		KALERT("%s: kf_open_locked failed\n", __FUNCTION__);
		ret = -ENODEV;
	}

	return ret;
}