ifdtool: Determine max regions from IFD

IFDv1 always has 8 regions, while IFDv2 always has 16 regions.

It's platform specific which regions are used or are reserved.
The 'SPI programming guide' as the name says is a guide only,
not a specification what the hardware actually does.
The best to do is not to rely on the guide, but detect how many
regions are present in the IFD and expose them all.

Very early IFDv2 chipsets, sometimes unofficially referred to as
IFDv1.5 platforms, only have 8 regions. To not corrupt the IFD when
operating on an IFDv1.5 detect how much space is actually present
in the IFD.

Fixes IFD corruption on Wellsburg/Lynxpoint when writing a new
flash layout.

Change-Id: I0e3f23ec580b8b8402eb1bf165e3995c8db633f1
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68780
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>
Reviewed-by: Christian Walter <christian.walter@9elements.com>

util/ifdtool/ifdtool.c

@@ -44,6 +44,8 @@
 #define PLATFORM_HAS_10GBE_0_REGION (platform == PLATFORM_DNV)
 #define PLATFORM_HAS_10GBE_1_REGION (platform == PLATFORM_DNV)
 
+static int max_regions_from_fdbar(const fdbar_t *fdb);
+
 static int ifd_version;
 static int chipset;
 static unsigned int max_regions = 0;
@@ -296,14 +298,16 @@ static int is_platform_ifd_2(void)
 
 static void check_ifd_version(char *image, int size)
 {
+	const fdbar_t *fdb = find_fd(image, size);
+
 	if (is_platform_ifd_2()) {
 		ifd_version = IFD_VERSION_2;
 		chipset = ifd2_platform_to_chipset(platform);
-		max_regions = MAX_REGIONS;
+		max_regions = MIN(max_regions_from_fdbar(fdb), MAX_REGIONS);
 	} else {
 		ifd_version = IFD_VERSION_1;
 		chipset = ifd1_guess_chipset(image, size);
-		max_regions = MAX_REGIONS_OLD;
+		max_regions = MIN(max_regions_from_fdbar(fdb), MAX_REGIONS_OLD);
 	}
 }
 
@@ -410,6 +414,49 @@ static void dump_region_layout(char *buf, size_t bufsize, unsigned int num,
 		region.base, region.limit, region_name_short(num));
 }
 
+static int sort_compare(const void *a, const void *b)
+{
+	return *(size_t *)a - *(size_t *)b;
+}
+
+/*
+ * IFDv1 always has 8 regions, while IFDv2 always has 16 regions.
+ *
+ * It's platform specific which regions are used or are reserved.
+ * The 'SPI programming guide' as the name says is a guide only,
+ * not a specification what the hardware actually does.
+ * The best to do is not to rely on the guide, but detect how many
+ * regions are present in the IFD and expose them all.
+ *
+ * Very early IFDv2 chipsets, sometimes unofficially referred to as
+ * IFDv1.5 platforms, only have 8 regions. To not corrupt the IFD when
+ * operating on an IFDv1.5 detect how much space is actually present
+ * in the IFD.
+ */
+static int max_regions_from_fdbar(const fdbar_t *fdb)
+{
+	const size_t fcba = (fdb->flmap0 & 0xff) << 4;
+	const size_t fmba = (fdb->flmap1 & 0xff) << 4;
+	const size_t frba = ((fdb->flmap0 >> 16) & 0xff) << 4;
+	const size_t fpsba = ((fdb->flmap1 >> 16) & 0xff) << 4;
+	const size_t flumap = 4096 - 256 - 4;
+	size_t sorted[5] = {fcba, fmba, frba, fpsba, flumap};
+
+	qsort(sorted, ARRAY_SIZE(sorted), sizeof(size_t), sort_compare);
+
+	for (size_t i = 0; i < 4; i++) {
+		/*
+		 * Find FRBA in the sorted array and determine the size of the
+		 * region by the start of the next region. Every region requires
+		 * 4 bytes of space.
+		 */
+		if (sorted[i] == frba)
+			return MIN((sorted[i+1] - sorted[i])/4, MAX_REGIONS);
+	}
+	/* Never reaches this point */
+	return 0;
+}
+
 static void dump_frba(const frba_t *frba)
 {
 	unsigned int i;