soc/intel/xeon_sp/cpx: Set the MRC "cold boot required" status bit

If bit 0 of byte 0x47 is set FSP will perform full memory training
even if previously saved data is supplied.

Up to and including FSP 2021 WW01 it was reset internally at the end
of PostMemoryInit. Starting with WW03 this is no longer the case and
Intel advised that this bit should be reset externally if valid MRC
data is present.

Change-Id: I9c4191d2fa2e0203b3464dcf40d845ede5f14c6b
Signed-off-by: Deomid "rojer" Ryabkov <rojer9@fb.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51230
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/src/soc/intel/xeon_sp/cpx/romstage.c b/src/soc/intel/xeon_sp/cpx/romstage.c
index c1cb0caeea..ad794c3b6f 100644
--- a/src/soc/intel/xeon_sp/cpx/romstage.c
+++ b/src/soc/intel/xeon_sp/cpx/romstage.c
@@ -8,14 +8,32 @@
 #include <fsp/util.h>
 #include <hob_iiouds.h>
 #include <hob_memmap.h>
+#include <pc80/mc146818rtc.h>
 #include <soc/ddr.h>
 #include <soc/romstage.h>
 #include <soc/pci_devs.h>
 #include <soc/intel/common/smbios.h>
+#include <stdbool.h>
 #include <string.h>
 
 #include "chip.h"
 
+/*
+ * Address of the MRC status byte in CMOS. Should be reserved
+ * in mainboards' cmos.layout and not covered by checksum.
+ */
+#define CMOS_OFFSET_MRC_STATUS 0x47
+
+#if CONFIG(USE_OPTION_TABLE)
+#include "option_table.h"
+#if CMOS_VSTART_mrc_status != CMOS_OFFSET_MRC_STATUS * 8
+#error "CMOS start for CPX-SP MRC status byte is not correct, check your cmos.layout"
+#endif
+#if CMOS_VLEN_mrc_status != 8
+#error "CMOS length for CPX-SP MRC status byte is not correct, check your cmos.layout"
+#endif
+#endif
+
 void __weak mainboard_memory_init_params(FSPM_UPD *mupd)
 {
 	/* Default weak implementation */
@@ -124,6 +142,16 @@ void save_dimm_info(void)
 	printk(BIOS_DEBUG, "%d DIMMs found\n", mem_info->dimm_cnt);
 }
 
+static void set_cmos_mrc_cold_boot_flag(bool cold_boot_required)
+{
+	uint8_t mrc_status = cmos_read(CMOS_OFFSET_MRC_STATUS);
+	uint8_t new_mrc_status = (mrc_status & 0xfe) | cold_boot_required;
+	printk(BIOS_SPEW, "MRC status: 0x%02x want 0x%02x\n", mrc_status, new_mrc_status);
+	if (new_mrc_status != mrc_status) {
+		cmos_write(new_mrc_status, CMOS_OFFSET_MRC_STATUS);
+	}
+}
+
 void platform_fsp_memory_init_params_cb(FSPM_UPD *mupd, uint32_t version)
 {
 	FSPM_CONFIG *m_cfg = &mupd->FspmConfig;
@@ -190,4 +218,7 @@ void platform_fsp_memory_init_params_cb(FSPM_UPD *mupd, uint32_t version)
 	m_cfg->isocEn = 0;
 
 	mainboard_memory_init_params(mupd);
+
+	/* Adjust the "cold boot required" flag in CMOS. */
+	set_cmos_mrc_cold_boot_flag(!mupd->FspmArchUpd.NvsBufferPtr);
 }