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serial: qcom-geni: fix hard lockup on buffer flush

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The Qualcomm GENI serial driver does not handle buffer flushing and used
to continue printing discarded characters when the circular buffer was
cleared. Since commit 1788cf6a91 ("tty: serial: switch from circ_buf
to kfifo") this instead results in a hard lockup due to
qcom_geni_serial_send_chunk_fifo() spinning indefinitely in the
interrupt handler.

This is easily triggered by interrupting a command such as dmesg in a
serial console but can also happen when stopping a serial getty on
reboot.

Implement the flush_buffer() callback and use it to cancel any active TX
command when the write buffer has been emptied.

Reported-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/lkml/20240610222515.3023730-1-dianders@chromium.org/
Fixes: 1788cf6a91 ("tty: serial: switch from circ_buf to kfifo")
Fixes: a1fee899e5 ("tty: serial: qcom_geni_serial: Fix softlock")
Cc: stable@vger.kernel.org	# 5.0
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20240704101805.30612-3-johan+linaro@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johan Hovold 2024-07-04 12:18:04 +02:00 committed by Greg Kroah-Hartman
parent 947cc4ecc0
commit 507786c51c
1 changed files with 13 additions and 3 deletions
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16
drivers/tty/serial/qcom_geni_serial.c
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@ -906,13 +906,17 @@ static void qcom_geni_serial_handle_tx_fifo(struct uart_port *uport,
else
pending = kfifo_len(&tport->xmit_fifo);
/* All data has been transmitted and acknowledged as received */
if (!pending && !status && done) {
/* All data has been transmitted or command has been cancelled */
if (!pending && done) {
qcom_geni_serial_stop_tx_fifo(uport);
goto out_write_wakeup;
}
avail = port->tx_fifo_depth - (status & TX_FIFO_WC);
if (active)
avail = port->tx_fifo_depth - (status & TX_FIFO_WC);
else
avail = port->tx_fifo_depth;
avail *= BYTES_PER_FIFO_WORD;
chunk = min(avail, pending);
@ -1091,6 +1095,11 @@ static void qcom_geni_serial_shutdown(struct uart_port *uport)
qcom_geni_serial_cancel_tx_cmd(uport);
}
static void qcom_geni_serial_flush_buffer(struct uart_port *uport)
{
qcom_geni_serial_cancel_tx_cmd(uport);
}
static int qcom_geni_serial_port_setup(struct uart_port *uport)
{
struct qcom_geni_serial_port *port = to_dev_port(uport);
@ -1547,6 +1556,7 @@ static const struct uart_ops qcom_geni_console_pops = {
.request_port = qcom_geni_serial_request_port,
.config_port = qcom_geni_serial_config_port,
.shutdown = qcom_geni_serial_shutdown,
.flush_buffer = qcom_geni_serial_flush_buffer,
.type = qcom_geni_serial_get_type,
.set_mctrl = qcom_geni_serial_set_mctrl,
.get_mctrl = qcom_geni_serial_get_mctrl,