text: // license:BSD-3-Clause
  // copyright-holders:Ryan Holtz
  /*****************************************************************************
  
      SunPlus SPG2xx-series SoC peripheral emulation (System DMA)
  
  **********************************************************************/
  
  #include "emu.h"
  #include "spg2xx_sysdma.h"
  
  DEFINE_DEVICE_TYPE(SPG2XX_SYSDMA, spg2xx_sysdma_device, "spg2xx_sysdma", "SPG240-series System-on-a-Chip System DMA")
  
  #define LOG_DMA             (1U << 9)
  #define LOG_ALL             (LOG_DMA)
  
  #define VERBOSE             (0)
  #include "logmacro.h"
  
  
  
  spg2xx_sysdma_device::spg2xx_sysdma_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
  	: device_t(mconfig, SPG2XX_SYSDMA, tag, owner, clock)
  	, m_cpu(*this, finder_base::DUMMY_TAG)
  {
  }
  
  void spg2xx_sysdma_device::device_start()
  {
  	save_item(NAME(m_dma_regs));
  }
  
  void spg2xx_sysdma_device::device_reset()
  {
  	memset(m_dma_regs, 0, 0x4 * sizeof(uint16_t));
  }
  
  /*************************
  *    Machine Hardware    *
  *************************/
  
  uint16_t spg2xx_sysdma_device::dma_r(offs_t offset)
  {
  	offset &= 0x3;
  
  	uint16_t val = m_dma_regs[offset];
  	switch (offset)
  	{
  
  	case 0x000: // DMA Source (L)
  		LOGMASKED(LOG_DMA, "dma_r: DMA Source (lo) = %04x\n", val);
  		break;
  
  	case 0x001: // DMA Source (H)
  		LOGMASKED(LOG_DMA, "dma_r: DMA Source (hi) = %04x\n", val);
  		break;
  
  	case 0x002: // DMA Length
  		LOGMASKED(LOG_DMA, "dma_r: DMA Length = %04x\n", 0);
  		val = 0;
  		break;
  
  	case 0x003: // DMA Destination
  		LOGMASKED(LOG_DMA, "dma_r: DMA Dest = %04x\n", val);
  		break;
  	}
  
  	return val;
  }
  
  void spg2xx_sysdma_device::dma_w(offs_t offset, uint16_t data)
  {
  	offset &= 0x3;
  
  	switch (offset)
  	{
  	case 0x000: // DMA Source (lo)
  		LOGMASKED(LOG_DMA, "dma_w: DMA Source (lo) = %04x\n", data);
  		m_dma_regs[offset] = data;
  		break;
  
  	case 0x001: // DMA Source (hi)
  		LOGMASKED(LOG_DMA, "dma_w: DMA Source (hi) = %04x\n", data);
  		m_dma_regs[offset] = data;
  		break;
  
  	case 0x002: // DMA Length
  		LOGMASKED(LOG_DMA, "dma_w: DMA Length = %04x\n", data);
  		if (!(data & 0xc000))  // jak_dora writes 0xffff here which ends up trashing registers etc. why? such writes can't be valid
  			do_cpu_dma(data);
  		break;
  
  	case 0x003: // DMA Destination
  		LOGMASKED(LOG_DMA, "dma_w: DMA Dest = %04x\n", data);
  		m_dma_regs[offset] = data;
  		break;
  	}
  }
  
  void spg2xx_sysdma_device::do_cpu_dma(uint32_t len)
  {
  	address_space &mem = m_cpu->space(AS_PROGRAM);
  
  	uint32_t src = ((m_dma_regs[0x001] & 0x3f) << 16) | m_dma_regs[0x000];
  	uint32_t dst = m_dma_regs[0x003] & 0x3fff;
  
  	for (uint32_t j = 0; j < len; j++)
  	{
  		mem.write_word((dst + j) & 0x3fff, mem.read_word(src + j));
  	}
  
  	src += len;
  	m_dma_regs[0x000] = (uint16_t)src;
  	m_dma_regs[0x001] = (src >> 16) & 0x3f;
  	m_dma_regs[0x002] = 0;
  	m_dma_regs[0x003] = (dst + len) & 0x3fff;
  }
  