soc/fsp_broadwell_de: Implement SMBus read/write over IMC

Add read/write functions to hook it up with existing SPD retrieval code.

Signed-off-by: Andrey Petrov <anpetrov@fb.com>
Change-Id: I9f5993dc795badf72751a4e6c9d974119a653e30
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34679
Reviewed-by: David Hendricks <david.hendricks@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/fsp_broadwell_de/Makefile.inc

@@ -14,6 +14,7 @@ subdirs-y += ../../../lib/fsp
 romstage-y += gpio.c
 romstage-y += memmap.c
 romstage-y += tsc_freq.c
+romstage-y += smbus-imc.c
 
 postcar-y += tsc_freq.c
 

src/soc/intel/fsp_broadwell_de/include/soc/pci_devs.h

@@ -126,4 +126,9 @@
 #define SMM_FUNC		0x06
 #define SMM_DEV_FUNC		PCI_DEVFN(SMM_DEV, SMM_FUNC)
 
+#define IMC_DEV0		19
+#define IMC_FUNC0		0
+
+#define IMC_DEV			PCI_DEV(QPI_BUS, IMC_DEV0, IMC_FUNC0)
+
 #endif /* _SOC_PCI_DEVS_H_ */

src/soc/intel/fsp_broadwell_de/smbus-imc.c

@@ -0,0 +1,59 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2019 Facebook, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <stddef.h>
+#include <console/console.h>
+#include <device/pci_def.h>
+#include <device/early_smbus.h>
+#include <intelblocks/imc.h>
+#include <soc/pci_devs.h>
+#include <spd.h>
+
+/* read word, return value on success */
+uint16_t smbus_read_word(u32 smbus_dev, u8 addr, u8 offset)
+{
+	uint16_t res = 0;
+
+	if (imc_smbus_spd_xfer(IMC_DEV, addr, offset, IMC_DEVICE_EEPROM, IMC_DATA_WORD,
+			       IMC_CONTROLLER_ID0, IMC_READ, &res)
+	    == 0) {
+		return res;
+	}
+	return 0;
+}
+
+/* read byte, return value on success */
+uint8_t smbus_read_byte(u32 smbus_dev, u8 addr, u8 offset)
+{
+	uint16_t res = 0;
+
+	if (imc_smbus_spd_xfer(IMC_DEV, addr, offset, IMC_DEVICE_EEPROM, IMC_DATA_BYTE,
+			       IMC_CONTROLLER_ID0, IMC_READ, &res)
+	    == 0) {
+		return res;
+	}
+	return 0;
+}
+
+/* write byte, return 0 on success, -1 otherwise */
+uint8_t smbus_write_byte(u32 smbus_dev, u8 addr, u8 offset, u8 value)
+{
+	if (imc_smbus_spd_xfer(IMC_DEV, addr, offset, IMC_DEVICE_WP_EEPROM, IMC_DATA_BYTE,
+			       IMC_CONTROLLER_ID0, IMC_WRITE, &value)
+	    == 0) {
+		return 0;
+	}
+	return -1;
+}