Patrick Georgi (pgeorgi@google.com) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/16882
-gerrit
commit e3e5a5e1719aa02076bbca01805b1b91478b6b74 Author: Brian Norris briannorris@chromium.org Date: Wed Sep 21 18:16:54 2016 -0700
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 --- src/mainboard/google/gru/mainboard.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/src/mainboard/google/gru/mainboard.c b/src/mainboard/google/gru/mainboard.c index 8b9f595..ae2c339 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. @@ -236,6 +246,7 @@ static void setup_usb(void)
static void mainboard_init(device_t dev) { + deassert_wifi_power(); configure_sdmmc(); configure_emmc(); configure_codec();