g: tell between C and D and P SKUs of the H1B2 chip

There are three different H1 B2 chips SKUs in the wild now, one
version is for clamshell Chromebooks, one is for experimental build of
Poppy and one for detachable devices.

The SKUs differ by some fuse settings, as outlined by the comment in
the code.

This patch maps fuse settings into the chip revision string and also
makes sure that the revision is determined once and then used for all
following invocations of system_get_chip_revision().

BRANCH=none
BUG=chrome-os-partner:59833
TEST=verified that on dev boards with three different H1 B2 SKUs the
      revision is reported as expected (B2-C, B2-D and B2-P).

Change-Id: I7d588d7326c28e9fa4921351254ad60a21c3f6b8
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/426344
Reviewed-by: Marius Schilder <mschilder@chromium.org>
Reviewed-by: Carl Hamilton <carlh@chromium.org>

1 files changed, 49 insertions, 2 deletions

diff --git a/chip/g/system.c b/chip/g/system.c
index a6a67cc5f1..8bc24040d1 100644
--- a/chip/g/system.c
+++ b/chip/g/system.c
@@ -147,10 +147,41 @@ const char *system_get_chip_name(void)
 	return "cr50";
 }
 
-const char *system_get_chip_revision(void)
+/*
+ * There are three versions of B2 H1s outhere in the wild so far: chromebook,
+ * poppy and detachable. The following registers are different in those
+ * three versions in the following way:
+ *
+ *   register                chromebook          poppy     detachable
+ *--------------------------------------------------------------------
+ * RBOX_KEY_COMBO0_VAL          0xc0             0x80        0xc0
+ * RBOX_POL_KEY1_IN             0x01             0x00        0x00
+ * RBOX_KEY_COMBO0_HOLD         0x00             0x00        0x59
+ */
+
+static const struct {
+	uint32_t  register_values;
+	const char *revision_str;
+} rev_map[] = {
+	{0xc00100, "B2-C"},	/* Chromebook. */
+	{0x800000, "B2-P"},	/* Poppy (a one off actually). */
+	{0xc00059, "B2-D"},	/* Detachable. */
+};
+
+/* Return a value which allows to identify the fuse setting of this chip. */
+static uint32_t get_fuse_set_id(void)
+{
+	return  (GREAD_FIELD(FUSE, RBOX_KEY_COMBO0_VAL, VAL) << 16) |
+		(GREAD_FIELD(FUSE, RBOX_POL_KEY1_IN, VAL) << 8) |
+		GREAD_FIELD(FUSE, RBOX_KEY_COMBO0_HOLD, VAL);
+}
+
+static const char *get_revision_str(void)
 {
 	int build_date = GR_SWDP_BUILD_DATE;
 	int build_time = GR_SWDP_BUILD_TIME;
+	uint32_t register_vals;
+	int i;
 
 	if ((build_date != GC_SWDP_BUILD_DATE_DEFAULT) ||
 	    (build_time != GC_SWDP_BUILD_TIME_DEFAULT))
@@ -159,13 +190,29 @@ const char *system_get_chip_revision(void)
 	switch (GREAD_FIELD(PMU, CHIP_ID, REVISION)) {
 	case 3:
 		return "B1";
+
 	case 4:
-		return "B2";
+		register_vals = get_fuse_set_id();
+		for (i = 0; i < ARRAY_SIZE(rev_map); i++)
+			if (rev_map[i].register_values == register_vals)
+				return rev_map[i].revision_str;
+
+		return "B2-?";
 	}
 
 	return "B?";
 }
 
+const char *system_get_chip_revision(void)
+{
+	static const char *revision_str;
+
+	if (!revision_str)
+		revision_str = get_revision_str();
+
+	return revision_str;
+}
+
 /* TODO(crosbug.com/p/33822): Where can we store stuff persistently? */
 int system_get_vbnvcontext(uint8_t *block)
 {