The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x 507786c51ccf8df726df804ae316a8c52537b407 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024071556-cognition-backstab-964b@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

507786c51ccf ("serial: qcom-geni: fix hard lockup on buffer flush") 2aaa43c70778 ("tty: serial: qcom-geni-serial: add support for serial engine DMA") 40ec6d41c841 ("tty: serial: qcom-geni-serial: use of_device_id data") 0626afe57b1f ("tty: serial: qcom-geni-serial: drop the return value from handle_rx") bd7955840cbe ("tty: serial: qcom-geni-serial: refactor qcom_geni_serial_send_chunk_fifo()") d420fb491cbc ("tty: serial: qcom-geni-serial: split out the FIFO tx code") fe6a00e8fcbe ("tty: serial: qcom-geni-serial: refactor qcom_geni_serial_isr()") 00ce7c6e86b5 ("tty: serial: qcom-geni-serial: improve the to_dev_port() macro") 6cde11dbf4b6 ("tty: serial: qcom-geni-serial: align #define values") 68c6bd92c86c ("tty: serial: qcom-geni-serial: remove unused symbols") d0fabb0dc1a6 ("tty: serial: qcom-geni-serial: drop unneeded forward definitions") 35781d8356a2 ("tty: serial: qcom-geni-serial: Add support for Hibernation feature") 654a8d6c93e7 ("tty: serial: qcom-geni-serial: Implement start_rx callback") c2194bc999d4 ("tty: serial: qcom-geni-serial: Remove uart frequency table. Instead, find suitable frequency with call to clk_round_rate.") d6efb3ac3e6c ("Merge tag 'tty-5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 507786c51ccf8df726df804ae316a8c52537b407 Mon Sep 17 00:00:00 2001 From: Johan Hovold johan+linaro@kernel.org 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 dianders@chromium.org 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 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

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,