mb/google/poppy/variants/nautilus: Bump VCC_SA voltage offset 75mV

Nautilus-Wifi with m3 AP got a halt issue during CTS test.

Nautilus-Wifi was FCS with Celeron AP first and also its PCB/BOM was
validated only with Celeron. Since Celeron deos not support turbo
boost mode, its steady power demend and lower CPU frequency may not
reflect the potential noise hidden inside the board.

Bumping VCC_SA voltage offset 75mV confirmed works to mitigate the
potential noise coupling to VCC_GT/SA, and we verified this change
makes this issue go away on Nautilus-Wifi board.

Nautilus-LTE doesn't show this issue, since it has 10L PCB, will have
better grounding and less noise/ripple than 8L PCB.

BUG=b:111417632
BRANCH=poppy
TEST=Verified CTS test pass without an issue.

Change-Id: Id13fcc36a5b6ed42620c66f57a7303f30bff1a50
Signed-off-by: Seunghwan Kim <sh_.kim@samsung.com>
Reviewed-on: https://review.coreboot.org/28439
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/src/mainboard/google/poppy/variants/nautilus/sku.c b/src/mainboard/google/poppy/variants/nautilus/sku.c
new file mode 100644
index 0000000000..55b118d847
--- /dev/null
+++ b/src/mainboard/google/poppy/variants/nautilus/sku.c
@@ -0,0 +1,43 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2018 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <baseboard/variants.h>
+#include <gpio.h>
+#include <variant/sku.h>
+
+uint32_t variant_board_sku(void)
+{
+#if ENV_ROMSTAGE
+	uint32_t sku_id = SKU_UNKNOWN;
+#else
+	static uint32_t sku_id = SKU_UNKNOWN;
+
+	if (sku_id != SKU_UNKNOWN)
+		return sku_id;
+#endif
+
+	/*
+	*  Nautilus uses GPP_B20 to determine SKU
+	*  0 - Wifi SKU
+	*  1 - LTE SKU
+	*/
+	gpio_input_pulldown(GPP_B20);
+	if (!gpio_get(GPP_B20))
+		sku_id = SKU_0_NAUTILUS;
+	else
+		sku_id = SKU_1_NAUTILUS_LTE;
+
+	return sku_id;
+}