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| author | Brian Norris <briannorris@chromium.org> | 2016-09-21 18:16:54 -0700 |
|---|---|---|
| committer | Patrick Georgi <pgeorgi@google.com> | 2016-10-07 17:55:39 +0200 |
| commit | e06a1b895c9905c53faaacf9286bafea7a3ef921 (patch) | |
| tree | 7e968b363b363e0df399b8f0d552bf49a685625a /src | |
| parent | 5d0847f7571b4b76a38b9ef5276ec0967f664833 (diff) | |
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')
| -rw-r--r-- | src/mainboard/google/gru/mainboard.c | 11 |
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(); |