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| author | Raul E Rangel <rrangel@chromium.org> | 2020-08-06 10:06:03 -0600 |
|---|---|---|
| committer | Commit Bot <commit-bot@chromium.org> | 2020-08-06 21:36:06 +0000 |
| commit | da7d2c02f003d4ec739987624a13a3e7ac639613 (patch) | |
| tree | 50866fd49273d9f9b6825262eec31ee211a97580 | |
| parent | 69bab88511023f0742aa2794698b3cab7f816eb6 (diff) | |
| download | chrome-ec-da7d2c02f003d4ec739987624a13a3e7ac639613.tar.gz | |
chip/npcx/lpc: Read HIKMST before HIKMDI
Reading HIKMDI causes the IBF flag to deassert and allows
the host to write a new byte into the input buffer. So if we
don't capture the status before reading HIKMDI we will race
with the host and get an invalid value for HIKMST.A20.
BUG=b:162539945, b:157617092, b:159282882
BRANCH=none
TEST=Boot ezkinil and make sure keyboard still functions.
Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: Ia8dcd18e3de31b4fa8c1742c7604d5c39e80dc51
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2341090
Commit-Queue: Edward Hill <ecgh@chromium.org>
Reviewed-by: Edward Hill <ecgh@chromium.org>
| -rw-r--r-- | chip/npcx/lpc.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/chip/npcx/lpc.c b/chip/npcx/lpc.c index 8572ce497d..b287ad8c36 100644 --- a/chip/npcx/lpc.c +++ b/chip/npcx/lpc.c @@ -518,11 +518,19 @@ static void handle_host_write(int is_cmd) /* KB controller input buffer full ISR */ void lpc_kbc_ibf_interrupt(void) { + uint8_t status; uint8_t ibf; /* If "command" input 0, else 1*/ if (lpc_keyboard_input_pending()) { + /* + * Reading HIKMDI causes the IBF flag to deassert and allows + * the host to write a new byte into the input buffer. So if we + * don't capture the status before reading HIKMDI we will race + * with the host and get an invalid value for HIKMST.A20. + */ + status = NPCX_HIKMST; ibf = NPCX_HIKMDI; - keyboard_host_write(ibf, (NPCX_HIKMST & 0x08) ? 1 : 0); + keyboard_host_write(ibf, (status & 0x08) ? 1 : 0); CPRINTS("ibf isr %02x", ibf); task_wake(TASK_ID_KEYPROTO); } else { |