diff options
| author | Nicolas Boichat <drinkcat@chromium.org> | 2017-12-27 13:50:16 +0800 |
|---|---|---|
| committer | chrome-bot <chrome-bot@chromium.org> | 2018-01-04 21:52:01 -0800 |
| commit | 51b62225209ca041749b3074db4cf4d10bd28b40 (patch) | |
| tree | 0d50a3051ad88d6552d232e102912da9fd99c9f8 | |
| parent | 6bbb5adab171d473f38f1ad9f8f0a1dafff30146 (diff) | |
| download | chrome-ec-51b62225209ca041749b3074db4cf4d10bd28b40.tar.gz | |
npcx/uart: Pull up communication line during transaction
Boards needs to define GPIO_EC_COMM_PU, which needs to be driven
high during EC-EC transaction. This makes sure that the line does
not go low, even when the base goes away during the transaction.
BRANCH=none
BUG=b:68954760
TEST=EC-EC communication works with this change.
TEST=With signal analyzer, check that UART line is always kept
high while transaction is in progress.
Change-Id: Iad7b26a9a93b674aa4fff0bc3a72a13e6782515d
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/845544
Reviewed-by: Randall Spangler <rspangler@chromium.org>
| -rw-r--r-- | chip/npcx/uart.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/chip/npcx/uart.c b/chip/npcx/uart.c index b7df104dbe..066c19b34a 100644 --- a/chip/npcx/uart.c +++ b/chip/npcx/uart.c @@ -326,6 +326,13 @@ int uart_alt_pad_write_read(uint8_t *tx, int tx_len, uint8_t *rx, int rx_len, altpad_tx_pos = 0; altpad_tx_len = tx_len; + /* + * Turn on additional pull-up during transaction: that prevents the line + * from going low in case the base gets disconnected during the + * transaction. See b/68954760. + */ + gpio_set_flags(GPIO_EC_COMM_PU, GPIO_OUTPUT | GPIO_HIGH); + uart_set_pad(UART_ALTERNATE_PAD); gpio_clear_pending_interrupt(GPIO_UART_MAIN_RX); gpio_enable_interrupt(GPIO_UART_MAIN_RX); @@ -354,6 +361,8 @@ int uart_alt_pad_write_read(uint8_t *tx, int tx_len, uint8_t *rx, int rx_len, ret = -EC_ERROR_TIMEOUT; out: + gpio_set_flags(GPIO_EC_COMM_PU, GPIO_INPUT); + altpad_rx_len = 0; altpad_rx_pos = 0; altpad_rx_buf = NULL; |