soc/software/liblitedram: add sdram debugging utilities

litex/soc/software/liblitedram/Makefile

@@ -1,7 +1,7 @@
 include ../include/generated/variables.mak
 include $(SOC_DIRECTORY)/software/common.mak
 
-OBJECTS = sdram.o bist.o
+OBJECTS = sdram.o bist.o sdram_dbg.o
 
 all: liblitedram.a
 

litex/soc/software/liblitedram/sdram_dbg.c

@@ -0,0 +1,87 @@
+#include <liblitedram/sdram_dbg.h>
+
+#include <string.h>
+#include <stdio.h>
+
+void error_stats_init(struct error_stats *stats) {
+	memset(stats, 0, sizeof(struct error_stats));
+}
+
+// TODO: Make the computations more generic
+#if SDRAM_PHY_DATABITS * SDRAM_PHY_XDR > 32
+#error "At most 32 databits SDR or 16 databits DDR supported"
+#endif
+void error_stats_update(struct error_stats *stats, struct memory_error err) {
+	unsigned int phase = (err.addr % (SDRAM_PHY_PHASES*4)) / 4;
+	unsigned int errors = err.data ^ err.ref;
+	for (int edge = 0; edge < SDRAM_PHY_XDR; ++edge) {
+		for (int bit = 0; bit < SDRAM_PHY_DATABITS; ++bit) {
+			unsigned int bitval = 1 << (SDRAM_PHY_DATABITS*edge + bit);
+			if ((errors & bitval) != 0) {
+				stats->phase[phase].edge[edge].dq[bit]++;
+			}
+		}
+	}
+}
+
+void error_stats_print(struct error_stats *stats) {
+	printf("        DQ:");
+	for (int bit = 0; bit < 16; ++bit) {
+		printf(" %5d", bit);
+	}
+	printf("\n");
+	for (int phase = 0; phase < 8; ++phase) {
+		for (int edge = 0; edge < 2; ++edge) {
+			unsigned int beat = 2*phase + edge;
+			printf("  beat[%2d]:", beat);
+			for (int bit = 0; bit < 16; ++bit) {
+				unsigned int dq_errors = stats->phase[phase].edge[edge].dq[bit];
+				printf(" %5d", dq_errors);
+			}
+			printf("\n");
+		}
+	}
+}
+
+void readback_init(struct readback *readback) {
+	readback->len = 0;
+}
+
+int readback_find(struct readback *readback, unsigned int addr) {
+	int left = 0;
+	int right = readback->len - 1;
+	while (left <= right) {
+		int mid = (left + right) / 2;
+		if (readback->errors[mid].addr == addr) {
+			return mid;
+		} else if (readback->errors[mid].addr < addr) {
+			left = mid + 1;
+		} else {
+			right = mid - 1;
+		}
+	}
+	return -1;
+}
+
+int readback_add(struct readback *readback, unsigned int max_len, struct memory_error error) {
+	if (readback->len >= max_len)
+		return 0;
+	readback->errors[readback->len++] = error;
+	return 1;
+}
+
+int readback_compare(struct readback *readback, struct readback *other, int verbose) {
+	int missing = 0;
+	for (unsigned int i = 0; i < readback->len ; ++i) {
+		struct memory_error *err = &readback->errors[i];
+		int at = readback_find(other, err->addr);
+		if (at < 0) {
+			if (verbose) {
+				printf("  Missing @0x%08x: 0x%08x vs 0x%08x\n",
+					err->addr, err->data, err->ref);
+			}
+			missing++;
+		}
+	}
+	return missing;
+}

litex/soc/software/liblitedram/sdram_dbg.h

@@ -0,0 +1,51 @@
+#ifndef __SDRAM_DBG_H
+#define __SDRAM_DBG_H
+
+#include <generated/sdram_phy.h>
+
+struct memory_error {
+	unsigned int addr;
+	unsigned int data;
+	unsigned int ref;
+};
+
+/* Provides error statictics per phase/edge/dq */
+struct error_stats {
+	struct {
+		struct {
+			unsigned int dq[SDRAM_PHY_DATABITS];
+		} edge[SDRAM_PHY_XDR];
+	} phase[SDRAM_PHY_PHASES];
+};
+
+void error_stats_init(struct error_stats *stats);
+void error_stats_update(struct error_stats *stats, struct memory_error error);
+void error_stats_print(struct error_stats *stats);
+
+/* Allows to store memory error information to compare several readbacks from memory.
+ *
+ * To achieve sensible results we need to store a lot of data, and we cannot use DRAM
+ * for that purpose (because we are debugging DRAM issues). This structure should be
+ * mapped to some memory region available in the SoC, ideally the SoC has some other
+ * memory that can be used, e.g. HyperRAM.
+ *
+ * This structure uses flexible array, so user must ensure number of errors fits into
+ * memory and must pass maximum size to readback_add when adding new entry.
+ */
+struct readback {
+	unsigned int len;
+	struct memory_error errors[];
+};
+
+#define READBACK_SIZE(n) (sizeof(struct readback) + (n) * sizeof(struct memory_error))
+
+void readback_init(struct readback *readback);
+// Uses binary search to find given address and return its index or -1 if not found.
+// The addresses int the whole readback array must be non-decreasing.
+int readback_find(struct readback *readback, unsigned int addr);
+// Add new entry if there is space (depending on max_len). Returns 1 if added new entry.
+int readback_add(struct readback *readback, unsigned int max_len, struct memory_error error);
+// Print errors that occured in `readback` that didn't occure in `other`. Returns number of errors.
+int readback_compare(struct readback *readback, struct readback *other, int verbose);
+
+#endif /* __SDRAM_DBG_H */