static const char *addr_of_char(unsigned char ch)
{
	static const char byte[] = {
		0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
		0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
		0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
		0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
		0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
		0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
		0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
		0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
		0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47,
		0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f,
		0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57,
		0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f,
		0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
		0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f,
		0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
		0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f,
		0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
		0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
		0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
		0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
		0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
		0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
		0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
		0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
		0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
		0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
		0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
		0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
		0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
		0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
		0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
		0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff,
	};
	return byte + ch;
}


static void print_debug_char(int c)
{
	asm volatile(
		"int $0x80"
		:
		: "a" (4), "b" (1), "c" (addr_of_char(c)), "d" (1)
		);

}
static void print_debug_nibble(unsigned nibble)
{
	unsigned char digit;
	digit = nibble + '0';
	if (digit > '9') {
		digit += 39;
	}
	print_debug_char(digit);
}
static void print_debug_hex8(unsigned char value)
{
	print_debug_nibble((value >> 4U) & 0x0fU);
	print_debug_nibble(value & 0x0fU);
}

static int smbus_read_byte(unsigned device, unsigned address)
{
	static const unsigned char dimm[] = {
0x80, 0x08, 0x07, 0x0d, 0x0a, 0x02, 0x48, 0x00, 0x04, 0x60, 0x70, 0x02, 0x82, 0x08, 0x08, 0x01,
0x0e, 0x04, 0x0c, 0x01, 0x02, 0x20, 0x00, 0x75, 0x70, 0x00, 0x00, 0x48, 0x30, 0x48, 0x2a, 0x40,
0x80, 0x80, 0x45, 0x45, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x33,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,

0x80, 0x08, 0x07, 0x0d, 0x0a, 0x02, 0x48, 0x00, 0x04, 0x60, 0x70, 0x02, 0x82, 0x08, 0x08, 0x01,
0x0e, 0x04, 0x0c, 0x01, 0x02, 0x20, 0x00, 0x75, 0x70, 0x00, 0x00, 0x48, 0x30, 0x48, 0x2a, 0x40,
0x80, 0x80, 0x45, 0x45, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x33,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
	};
	return dimm[(device << 8) + address];
}

static void spd_set_memclk(void)
{
	/* Compute the minimum cycle time for these dimms */
	unsigned min_cycle_time, min_latency;
	unsigned device;
	unsigned value;

	value = 0x50;
	min_cycle_time= 0x75;
	min_latency = 2;
	device = 0;


	/* Compute the least latency with the fastest clock supported
	 * by both the memory controller and the dimms.
	 */
	int new_cycle_time, new_latency;
	int index;
	int latencies;
	int latency;

	/* First find the supported CAS latencies
	 * Byte 18 for DDR SDRAM is interpreted:
	 * bit 0 == CAS Latency = 1.0
	 * bit 1 == CAS Latency = 1.5
	 * bit 2 == CAS Latency = 2.0
	 * bit 3 == CAS Latency = 2.5
	 * bit 4 == CAS Latency = 3.0
	 * bit 5 == CAS Latency = 3.5
	 * bit 6 == TBD
	 * bit 7 == TBD
	 */
	new_cycle_time = 0xa0;
	new_latency = 5;

	latencies = smbus_read_byte(device, 18);

	/* Compute the lowest cas latency supported */
	latency = __builtin_bsr(latencies) -2;

	/* Loop through and find a fast clock with a low latency */
	for(index = 0; index < 1; index++, latency++)
	{
		int value;

		if ((latency < 2) || (latency > 4) ||
			(!(latencies & (1 << latency)))) {
			continue;
		}
		value = smbus_read_byte(device, index);

		/* Only increase the latency if we decreas the clock */
		if ((value >= min_cycle_time) && (value < new_cycle_time)) {
			new_cycle_time = value;
			new_latency = latency;
			print_debug_hex8(device);
		}
	}
}
