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authorBrian Norris <briannorris@chromium.org>2016-09-21 18:16:54 -0700
committerPatrick Georgi <pgeorgi@google.com>2016-10-07 17:55:39 +0200
commite06a1b895c9905c53faaacf9286bafea7a3ef921 (patch)
tree7e968b363b363e0df399b8f0d552bf49a685625a /src/mainboard/google
parent5d0847f7571b4b76a38b9ef5276ec0967f664833 (diff)
downloadcoreboot-e06a1b895c9905c53faaacf9286bafea7a3ef921.tar.xz
google/gru: drive WLAN_MODULE_RST# low as early as possible
GPIO1_B3 (WLAN_MODULE_RST#) defaults as a pull-up input, but it is also "pulled up" by 1.8V_WLAN. However, 1.8V_WLAN remains low for some time during early boot. This leaves the signal floating somewhere in the middle. This has two potential issues: (1) we're leaking some power for some (hopefully) short period of time (2) we are possibly screwing with the Wifi power sequence; we aren't supposed to deassert PDn (i.e., MODULE_RST#) until all the rails have fully ramped for some period of time Neither of the above issues are likely to be significant, but it is nice to fix, I expect. BRANCH=gru BUG=chrome-os-partner:54026 TEST=measure WLAN_MODULE_RST# on scope at boot time Change-Id: Ia6af9ad6954ad8feeda33015e3f205842380939e Signed-off-by: Patrick Georgi <pgeorgi@chromium.org> Original-Commit-Id: 0e890a2787bf034d3358a33fc88c2dd8078593ab Original-Change-Id: I120e26ad0ca486a326874986e142dcaee965b62d Original-Signed-off-by: Brian Norris <briannorris@chromium.org> Original-Reviewed-on: https://chromium-review.googlesource.com/388009 Original-Reviewed-by: Douglas Anderson <dianders@chromium.org> Original-Reviewed-by: Julius Werner <jwerner@chromium.org> Reviewed-on: https://review.coreboot.org/16882 Tested-by: build bot (Jenkins) Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net> Reviewed-by: Martin Roth <martinroth@google.com>
Diffstat (limited to 'src/mainboard/google')
-rw-r--r--src/mainboard/google/gru/mainboard.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/src/mainboard/google/gru/mainboard.c b/src/mainboard/google/gru/mainboard.c
index b9d5355bf1..0b55e7faf7 100644
--- a/src/mainboard/google/gru/mainboard.c
+++ b/src/mainboard/google/gru/mainboard.c
@@ -29,6 +29,16 @@
#include "board.h"
+/*
+ * Wifi's PDN/RST line is pulled down by its (unpowered) voltage rails, but
+ * this reset pin is pulled up by default. Let's drive it low as early as we
+ * can.
+ */
+static void deassert_wifi_power(void)
+{
+ gpio_output(GPIO(1, B, 3), 0); /* Assert WLAN_MODULE_RST# */
+}
+
static void configure_emmc(void)
{
/* Host controller does not support programmable clock generator.
@@ -237,6 +247,7 @@ static void setup_usb(void)
static void mainboard_init(device_t dev)
{
+ deassert_wifi_power();
configure_sdmmc();
configure_emmc();
configure_codec();