x86: Implement a cache for Memory Reference Code parameters

The memory reference code takes a very long time to 'train' its SDRAM
interface, around half a second. To avoid this delay on every boot we can
store the parameters from the last training sessions to speed up the next.

Add an implementation of this, storing the training data in CMOS RAM and
SPI flash.

Signed-off-by: Simon Glass <sjg@chromium.org>

2 files changed, 54 insertions, 0 deletions

diff --git a/arch/x86/include/asm/arch-ivybridge/mrccache.h b/arch/x86/include/asm/arch-ivybridge/mrccache.h
new file mode 100644
index 0000000..968b2ef
--- /dev/null
+++ b/arch/x86/include/asm/arch-ivybridge/mrccache.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2014 Google, Inc
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef _ASM_ARCH_MRCCACHE_H
+#define _ASM_ARCH_MRCCACHE_H
+
+#define MRC_DATA_ALIGN		0x1000
+#define MRC_DATA_SIGNATURE	(('M' << 0) | ('R' << 8) | ('C' << 16) | \
+					('D'<<24))
+
+__packed struct mrc_data_container {
+	u32	signature;	/* "MRCD" */
+	u32	data_size;	/* Size of the 'data' field */
+	u32	checksum;	/* IP style checksum */
+	u32	reserved;	/* For header alignment */
+	u8	data[0];	/* Variable size, platform/run time dependent */
+};
+
+struct fmap_entry;
+struct spi_flash;
+
+/**
+ * mrccache_find_current() - find the latest MRC cache record
+ *
+ * This searches the MRC cache region looking for the latest record to use
+ * for setting up SDRAM
+ *
+ * @entry:	Information about the position and size of the MRC cache
+ * @return pointer to latest record, or NULL if none
+ */
+struct mrc_data_container *mrccache_find_current(struct fmap_entry *entry);
+
+/**
+ * mrccache_update() - update the MRC cache with a new record
+ *
+ * This writes a new record to the end of the MRC cache. If the new record is
+ * the same as the latest record then the write is skipped
+ *
+ * @sf:		SPI flash to write to
+ * @entry:	Position and size of MRC cache in SPI flash
+ * @cur:	Record to write
+ * @return 0 if updated, -EEXIST if the record is the same as the latest
+ * record, other error if SPI write failed
+ */
+int mrccache_update(struct spi_flash *sf, struct fmap_entry *entry,
+		    struct mrc_data_container *cur);
+
+#endif
diff --git a/arch/x86/include/asm/global_data.h b/arch/x86/include/asm/global_data.h
index 243ed5c..5ee06eb 100644
--- a/arch/x86/include/asm/global_data.h
+++ b/arch/x86/include/asm/global_data.h
@@ -65,6 +65,9 @@ struct arch_global_data {
 	struct mtrr_request mtrr_req[MAX_MTRR_REQUESTS];
 	int mtrr_req_count;
 	int has_mtrr;
+	/* MRC training data to save for the next boot */
+	char *mrc_output;
+	unsigned int mrc_output_len;
 };
 
 #endif