diff options
| author | Douglas Anderson <dianders@chromium.org> | 2020-08-06 22:19:08 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-08-18 13:25:52 +0200 |
| commit | d681a6e4e353958cba22faf2c48474ad1efa20c8 (patch) | |
| tree | 6017eadac7fbb4d4794a35ecf736f444e83b6092 /drivers/tty | |
| parent | bc5269ca765057a1b762e79a1cfd267cd7bf1c46 (diff) | |
serial: qcom_geni_serial: Fix recent kdb hang
The commit e42d6c3ec0c7 ("serial: qcom_geni_serial: Make kgdb work
even if UART isn't console") worked pretty well and I've been doing a
lot of debugging with it. However, recently I typed "dmesg" in kdb
and then held the space key down to scroll through the pagination. My
device hung. This was repeatable and I found that it was introduced
with the aforementioned commit.
It turns out that there are some strange boundary cases in geni where
in some weird situations it will signal RX_LAST but then will put 0 in
RX_LAST_BYTE. This means that the entire last FIFO entry is valid.
This weird corner case is handled in qcom_geni_serial_handle_rx()
where you can see that we only honor RX_LAST_BYTE if RX_LAST is set
_and_ RX_LAST_BYTE is non-zero. If either of these is not true we use
BYTES_PER_FIFO_WORD (4) for the size of the last FIFO word.
Let's fix kgdb. While at it, also use the proper #define for 4.
Fixes: e42d6c3ec0c7 ("serial: qcom_geni_serial: Make kgdb work even if UART isn't console")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Akash Asthana <akashast@codeaurora.org>
Link: https://lore.kernel.org/r/20200806221904.1.I4455ff86f0ef5281c2a0cd0a4712db614548a5ca@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | drivers/tty/serial/qcom_geni_serial.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c index 3aa29d201f54..31e57dd94032 100644 --- a/drivers/tty/serial/qcom_geni_serial.c +++ b/drivers/tty/serial/qcom_geni_serial.c @@ -361,11 +361,16 @@ static int qcom_geni_serial_get_char(struct uart_port *uport) return NO_POLL_CHAR; if (word_cnt == 1 && (status & RX_LAST)) + /* + * NOTE: If RX_LAST_BYTE_VALID is 0 it needs to be + * treated as if it was BYTES_PER_FIFO_WORD. + */ private_data->poll_cached_bytes_cnt = (status & RX_LAST_BYTE_VALID_MSK) >> RX_LAST_BYTE_VALID_SHFT; - else - private_data->poll_cached_bytes_cnt = 4; + + if (private_data->poll_cached_bytes_cnt == 0) + private_data->poll_cached_bytes_cnt = BYTES_PER_FIFO_WORD; private_data->poll_cached_bytes = readl(uport->membase + SE_GENI_RX_FIFOn); |