lib/spd_cache: add spd_cache common code

This patch adds some spd_cache functions. They are for implementing the
spd_cache. It's for reducing the SPD fetch time when device uses SODIMMs.
The MRC cache also includes SPD data, but there is no public header file
available to decode the struct of MRC. So SPD cache is another solution.

BUG=b:146457985
BRANCH=None
TEST=Build puff successfully and verified below two items.
     one DIMM save the boot time : 158ms
     two DIMM save the boot time : 265ms

Change-Id: Ia48aa022fabf8949960a50597185c9d821399522
Signed-off-by: Jamie Chen <jamie.chen@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40797
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: EricR Lai <ericr_lai@compal.corp-partner.google.com>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>

3 files changed, 246 insertions, 0 deletions

diff --git a/src/include/spd_cache.h b/src/include/spd_cache.h
new file mode 100644
index 0000000000..3270defba8
--- /dev/null
+++ b/src/include/spd_cache.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* This file is part of the coreboot project. */
+
+#ifndef __SPD_CACHE_H
+#define __SPD_CACHE_H
+
+#include <spd_bin.h>
+
+#define SPD_CACHE_FMAP_NAME	"RW_SPD_CACHE"
+#define SC_SPD_NUMS		(CONFIG_DIMM_MAX)
+#define SC_SPD_OFFSET(n)	(CONFIG_DIMM_SPD_SIZE * n)
+#define SC_CRC_OFFSET		(CONFIG_DIMM_MAX * CONFIG_DIMM_SPD_SIZE)
+#define SC_SPD_TOTAL_LEN	(CONFIG_DIMM_MAX * CONFIG_DIMM_SPD_SIZE)
+#define SC_SPD_LEN		(CONFIG_DIMM_SPD_SIZE)
+#define SC_CRC_LEN		(sizeof(uint16_t))
+
+enum cb_err update_spd_cache(struct spd_block *blk);
+enum cb_err load_spd_cache(uint8_t **spd_cache, size_t *spd_cache_sz);
+bool spd_cache_is_valid(uint8_t *spd_cache, size_t spd_cache_sz);
+bool check_if_dimm_changed(u8 *spd_cache, struct spd_block *blk);
+enum cb_err spd_fill_from_cache(uint8_t *spd_cache, struct spd_block *blk);
+
+#endif
diff --git a/src/lib/Makefile.inc b/src/lib/Makefile.inc
index 1fed543f70..b6d318e7a3 100644
--- a/src/lib/Makefile.inc
+++ b/src/lib/Makefile.inc
@@ -345,3 +345,5 @@ spd.bin-type := spd
 endif
 
 ramstage-y += uuid.c
+
+romstage-$(CONFIG_ROMSTAGE_SPD_SMBUS) += spd_cache.c
diff --git a/src/lib/spd_cache.c b/src/lib/spd_cache.c
new file mode 100644
index 0000000000..71dfaf1024
--- /dev/null
+++ b/src/lib/spd_cache.c
@@ -0,0 +1,221 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* This file is part of the coreboot project. */
+
+#include <assert.h>
+#include <console/console.h>
+#include <crc_byte.h>
+#include <fmap.h>
+#include <spd_cache.h>
+#include <spd_bin.h>
+#include <string.h>
+
+/*
+ * SPD_CACHE layout
+ *    +==========+ offset 0x00
+ *    |DIMM 1 SPD|   SPD data length is CONFIG_DIMM_SPD_SIZE.
+ *    +----------+ offset CONFIG_DIMM_SPD_SIZE * 1
+ *    |DIMM 2 SPD|
+ *    +----------+ offset CONFIG_DIMM_SPD_SIZE * 2
+ *         ...
+ *    +----------+ offset CONFIG_DIMM_SPD_SIZE * (N -1)
+ *    |DIMM N SPD|   N = CONFIG_DIMM_MAX
+ *    +----------+ offset CONFIG_DIMM_SPD_SIZE * CONFIG_DIMM_MAX
+ *    |  CRC 16  |   Use to verify the data correctness.
+ *    +==========+
+ *
+ *  The size of the RW_SPD_CACHE needs to be aligned with 4KiB.
+ */
+
+/*
+ * Use to update SPD cache.
+ *  *blk : the new SPD data will be stash into the cache.
+ *
+ *  return CB_SUCCESS , update SPD cache successfully.
+ *  return CB_ERR , update SPD cache unsuccessfully and the cache is invalid
+ */
+enum cb_err update_spd_cache(struct spd_block *blk)
+{
+	struct region_device rdev;
+	uint16_t data_crc = 0;
+	int i, j;
+
+	assert(blk->len <= SC_SPD_LEN);
+
+	if (fmap_locate_area_as_rdev_rw(SPD_CACHE_FMAP_NAME, &rdev)) {
+		printk(BIOS_ERR, "SPD_CACHE: Cannot access %s region\n", SPD_CACHE_FMAP_NAME);
+		return CB_ERR;
+	}
+
+	/* Erase whole area, it's for align with 4KiB which is the size of SPI rom sector. */
+	if (rdev_eraseat(&rdev, 0, region_device_sz(&rdev)) < 0) {
+		printk(BIOS_ERR, "SPD_CACHE: Cannot erase %s region\n", SPD_CACHE_FMAP_NAME);
+		return CB_ERR;
+	}
+
+	/* Write SPD data */
+	for (i = 0; i < SC_SPD_NUMS; i++) {
+		if (blk->spd_array[i] == NULL) {
+			/* If DIMM is not present, we calculate the CRC with 0xff. */
+			for (j = 0; j < SC_SPD_LEN; j++)
+				data_crc = crc16_byte(data_crc, 0xff);
+		} else {
+			if (rdev_writeat(&rdev, blk->spd_array[i], SC_SPD_OFFSET(i), blk->len)
+										< 0) {
+				printk(BIOS_ERR, "SPD_CACHE: Cannot write SPD data at %d\n",
+					SC_SPD_OFFSET(i));
+				return CB_ERR;
+			}
+
+			for (j = 0; j < blk->len; j++)
+				data_crc = crc16_byte(data_crc, blk->spd_array[i][j]);
+
+			/* If the blk->len < SC_SPD_LEN, we calculate the CRC with 0xff. */
+			if (blk->len < SC_SPD_LEN)
+				for (j = 0; j < (SC_SPD_LEN - (blk->len)); j++)
+					data_crc = crc16_byte(data_crc, 0xff);
+		}
+	}
+
+	/* Write the crc16 */
+	/* It must be the last step to ensure that the data is written correctly */
+	if (rdev_writeat(&rdev, &data_crc, SC_CRC_OFFSET, SC_CRC_LEN) < 0) {
+		printk(BIOS_ERR, "SPD_CACHE: Cannot write crc at 0x%04x\n", SC_CRC_OFFSET);
+		return CB_ERR;
+	}
+	return CB_SUCCESS;
+}
+
+/*
+ * Locate the RW_SPD_CACHE area in the fmap and read SPD_CACHE data.
+ *  return CB_SUCCESS ,if the SPD_CACHE data is ready and the pointer return at *spd_cache.
+ *  return CB_ERR ,if it cannot locate RW_SPD_CACHE area in the fmap or data cannot be read.
+ */
+enum cb_err load_spd_cache(uint8_t **spd_cache, size_t *spd_cache_sz)
+{
+	struct region_device rdev;
+
+	if (fmap_locate_area_as_rdev(SPD_CACHE_FMAP_NAME, &rdev) < 0) {
+		printk(BIOS_ERR, "SPD_CACHE: Cannot find %s region\n", SPD_CACHE_FMAP_NAME);
+		return CB_ERR;
+	}
+
+	/* Assume boot device is memory mapped. */
+	assert(CONFIG(BOOT_DEVICE_MEMORY_MAPPED));
+	*spd_cache = rdev_mmap_full(&rdev);
+
+	if (*spd_cache == NULL)
+		return CB_ERR;
+
+	*spd_cache_sz = region_device_sz(&rdev);
+
+	/* SPD cache found */
+	printk(BIOS_INFO, "SPD_CACHE: cache found, size 0x%zx\n", *spd_cache_sz);
+
+	return CB_SUCCESS;
+}
+
+/* Use to verify the cache data is valid. */
+bool spd_cache_is_valid(uint8_t *spd_cache, size_t spd_cache_sz)
+{
+	uint16_t data_crc = 0;
+	int i;
+
+	if (spd_cache_sz < SC_SPD_TOTAL_LEN + SC_CRC_LEN)
+		return false;
+
+	/* Check the spd_cache crc */
+	for (i = 0; i < SC_SPD_TOTAL_LEN; i++)
+		data_crc = crc16_byte(data_crc, *(spd_cache + i));
+
+	return *(uint16_t *)(spd_cache + SC_CRC_OFFSET) == data_crc;
+}
+
+/*
+ * Check if the DIMM is preset in cache.
+ *  return true , DIMM is present.
+ *  return false, DIMM is not present.
+ */
+static bool get_cached_dimm_present(uint8_t *spd_cache, uint8_t idx)
+{
+	if (*(uint16_t *)(spd_cache + SC_SPD_OFFSET(idx)) == 0xffff)
+		return false;
+	else
+		return true;
+}
+
+/*
+ * Use to check if the SODIMM is changed.
+ *  spd_cache : it's a valid SPD cache.
+ *  blk       : it must include the smbus addresses of SODIMM.
+ */
+bool check_if_dimm_changed(u8 *spd_cache, struct spd_block *blk)
+{
+	int i;
+	u32 sn;
+	bool dimm_present_in_cache;
+	bool dimm_changed = false;
+	/* Check if the dimm is the same with last system boot. */
+	for (i = 0; i < SC_SPD_NUMS && dimm_changed == false; i++) {
+		/* Return true if any error happened here. */
+		if (get_spd_sn(blk->addr_map[i], &sn) == CB_ERR)
+			return true;
+		dimm_present_in_cache = get_cached_dimm_present(spd_cache, i);
+		/* Dimm is not present now. */
+		if (sn == 0xffffffff) {
+			if (dimm_present_in_cache == false)
+				printk(BIOS_NOTICE, "SPD_CACHE: DIMM%d is not present\n", i);
+			else {
+				printk(BIOS_NOTICE, "SPD_CACHE: DIMM%d lost\n", i);
+				dimm_changed = true;
+			}
+		} else { /* Dimm is present now. */
+			if (dimm_present_in_cache == true) {
+				if (memcmp(&sn, spd_cache + SC_SPD_OFFSET(i) + DDR4_SPD_SN_OFF,
+						SPD_SN_LEN) == 0)
+					printk(BIOS_NOTICE, "SPD_CACHE: DIMM%d is the same\n",
+											i);
+				else {
+					printk(BIOS_NOTICE, "SPD_CACHE: DIMM%d is new one\n",
+											i);
+					dimm_changed = true;
+				}
+			} else {
+				printk(BIOS_NOTICE, "SPD_CACHE: DIMM%d is new one\n", i);
+				dimm_changed = true;
+			}
+		}
+	}
+	return dimm_changed;
+}
+
+/* Use to fill the struct spd_block with cache data.*/
+enum cb_err spd_fill_from_cache(uint8_t *spd_cache, struct spd_block *blk)
+{
+	int i;
+	u8 dram_type;
+
+	/* Find the first present SPD */
+	for (i = 0; i < SC_SPD_NUMS; i++)
+		if (get_cached_dimm_present(spd_cache, i) == true)
+			break;
+
+	if (i == SC_SPD_NUMS) {
+		printk(BIOS_ERR, "SPD_CACHE: No DIMM is present.\n");
+		return CB_ERR;
+	}
+
+	dram_type = *(spd_cache + SC_SPD_OFFSET(i) + SPD_DRAM_TYPE);
+
+	if (dram_type == SPD_DRAM_DDR4)
+		blk->len = SPD_PAGE_LEN_DDR4;
+	else
+		blk->len = SPD_PAGE_LEN;
+
+	for (i = 0; i < SC_SPD_NUMS; i++)
+		if (get_cached_dimm_present(spd_cache, i) == true)
+			blk->spd_array[i] = spd_cache + SC_SPD_OFFSET(i);
+		else
+			blk->spd_array[i] = NULL;
+
+	return CB_SUCCESS;
+}