From 507786c51ccf8df726df804ae316a8c52537b407 Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Thu, 4 Jul 2024 12:18:04 +0200 Subject: [PATCH] serial: qcom-geni: fix hard lockup on buffer flush 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 1788cf6a91d9 ("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 Link: https://lore.kernel.org/lkml/20240610222515.3023730-1-dianders@chromium.org/ Fixes: 1788cf6a91d9 ("tty: serial: switch from circ_buf to kfifo") Fixes: a1fee899e5be ("tty: serial: qcom_geni_serial: Fix softlock") Cc: stable@vger.kernel.org # 5.0 Signed-off-by: Johan Hovold Link: https://lore.kernel.org/r/20240704101805.30612-3-johan+linaro@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/qcom_geni_serial.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c index a41360d34790..b2bbd2d79dbb 100644 --- a/drivers/tty/serial/qcom_geni_serial.c +++ b/drivers/tty/serial/qcom_geni_serial.c @@ -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,