intel/common/smbus: increase spd read performance

This change increases the spd read performance by using smbus word
access.

BUG=b:67021853
TEST=boot to os and find 80~100 ms boot time improvement on one dimm

Change-Id: I98fe67642d8ccd428bccbca7f6390331d6055d14
Signed-off-by: Kane Chen <kane.chen@intel.com>
Reviewed-on: https://review.coreboot.org/22072
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/Kconfig

@@ -1212,6 +1212,9 @@ config DIMM_SPD_SIZE
 	  Total SPD size that will be used for DIMM.
 	  Ex: DDR3 256, DDR4 512.
 
+config SPD_READ_BY_WORD
+	bool
+
 config BOARD_ID_AUTO
 	bool
 	default n

src/include/device/early_smbus.h

@@ -63,6 +63,7 @@ void smbus_reset(u32 smbus_dev);
 int smbus_print_error(u32 smbus_dev, u8 host_status, int loops);
 int smbus_is_busy(u32 smbus_dev);
 int smbus_wait_until_ready(u32 smbus_dev);
+u16 smbus_read_word(u32 smbus_dev, u8 addr, u8 offset);
 u8 smbus_read_byte(u32 smbus_dev, u8 addr, u8 offset);
 u8 smbus_write_byte(u32 smbus_dev, u8 addr, u8 offset, u8 value);
 void smbus_delay(void);

src/lib/spd_bin.c

@@ -125,26 +125,40 @@ int get_spd_cbfs_rdev(struct region_device *spd_rdev, u8 spd_index)
 							CONFIG_DIMM_SPD_SIZE);
 }
 
-static void get_spd(u8 *spd, u8 addr)
+static void smbus_read_spd(u8 *spd, u8 addr)
 {
 	u16 i;
-	if (smbus_read_byte(0, addr, 0)  == 0xff) {
+	u8 step = 1;
+
+	if (IS_ENABLED(CONFIG_SPD_READ_BY_WORD))
+		step = sizeof(uint16_t);
+
+	for (i = 0; i < SPD_PAGE_LEN; i += step) {
+		if (IS_ENABLED(CONFIG_SPD_READ_BY_WORD))
+			((u16*)spd)[i / sizeof(uint16_t)] =
+				 smbus_read_word(0, addr, i);
+		else
+			spd[i] = smbus_read_byte(0, addr, i);
+	}
+}
+
+static void get_spd(u8 *spd, u8 addr)
+{
+	if (smbus_read_byte(0, addr, 0) == 0xff) {
 		printk(BIOS_INFO, "No memory dimm at address %02X\n",
 			addr << 1);
 		/* Make sure spd is zeroed if dimm doesn't exist. */
 		memset(spd, 0, CONFIG_DIMM_SPD_SIZE);
 		return;
 	}
+	smbus_read_spd(spd, addr);
 
-	for (i = 0; i < SPD_PAGE_LEN; i++)
-		spd[i] = smbus_read_byte(0, addr, i);
 	/* Check if module is DDR4, DDR4 spd is 512 byte. */
 	if (spd[SPD_DRAM_TYPE] == SPD_DRAM_DDR4 &&
-		CONFIG_DIMM_SPD_SIZE >= SPD_DRAM_DDR4) {
+		CONFIG_DIMM_SPD_SIZE > SPD_PAGE_LEN) {
 		/* Switch to page 1 */
 		smbus_write_byte(0, SPD_PAGE_1, 0, 0);
-		for (i = 0; i < SPD_PAGE_LEN; i++)
-			spd[i+SPD_PAGE_LEN] = smbus_read_byte(0, addr, i);
+		smbus_read_spd(spd + SPD_PAGE_LEN, addr);
 		/* Restore to page 0 */
 		smbus_write_byte(0, SPD_PAGE_0, 0, 0);
 	}

src/soc/intel/common/block/smbus/smbus_early.c

@@ -36,6 +36,11 @@ static const struct reg_script smbus_init_script[] = {
 	REG_SCRIPT_END,
 };
 
+u16 smbus_read_word(u32 smbus_dev, u8 addr, u8 offset)
+{
+	return smbus_read16(SMBUS_IO_BASE, addr, offset);
+}
+
 u8 smbus_read_byte(u32 smbus_dev, u8 addr, u8 offset)
 {
 	return smbus_read8(SMBUS_IO_BASE, addr, offset);

src/soc/intel/common/block/smbus/smbuslib.c

@@ -135,3 +135,44 @@ int smbus_write8(unsigned int smbus_base, unsigned int device,
 
 	return 0;
 }
+
+int smbus_read16(unsigned int smbus_base, unsigned int device,
+	unsigned int address)
+{
+	unsigned char global_status_register;
+	unsigned short data;
+
+	if (smbus_wait_till_ready(smbus_base) < 0)
+		return SMBUS_WAIT_UNTIL_READY_TIMEOUT;
+
+	/* Set up transaction */
+	/* Disable interrupts */
+	outb(inb(smbus_base + SMBHSTCTL) & ~1, smbus_base + SMBHSTCTL);
+	/* Set the device I'm talking to */
+	outb(((device & 0x7f) << 1) | 1, smbus_base + SMBXMITADD);
+	/* Set the command/address... */
+	outb(address & 0xff, smbus_base + SMBHSTCMD);
+	/* Set up for a word data read */
+	outb((inb(smbus_base + SMBHSTCTL) & 0xe3) | (0x3 << 2),
+		(smbus_base + SMBHSTCTL));
+	/* Clear any lingering errors, so the transaction will run */
+	outb(inb(smbus_base + SMBHSTSTAT), smbus_base + SMBHSTSTAT);
+
+	/* Start the command */
+	outb((inb(smbus_base + SMBHSTCTL) | 0x40),
+	     smbus_base + SMBHSTCTL);
+
+	/* Poll for transaction completion */
+	if (smbus_wait_till_done(smbus_base) < 0)
+		return SMBUS_WAIT_UNTIL_DONE_TIMEOUT;
+
+	global_status_register = inb(smbus_base + SMBHSTSTAT);
+	/* Ignore the "In Use" status... */
+	if ((global_status_register & ~(3 << 5)) != (1 << 1))
+		return SMBUS_ERROR;
+
+	/* Read results of transaction */
+	data = inw(smbus_base + SMBHSTDAT0);
+
+	return data;
+}

src/soc/intel/common/block/smbus/smbuslib.h

@@ -34,5 +34,7 @@ int smbus_read8(unsigned int smbus_base, unsigned int device,
 		unsigned int address);
 int smbus_write8(unsigned int smbus_base, unsigned int device,
 		unsigned int address, unsigned int data);
+int smbus_read16(unsigned int smbus_base, unsigned int device,
+		unsigned int address);
 
 #endif	/* SOC_INTEL_COMMON_BLOCK_SMBUS__LIB_H */