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 f97cdbbf187fefcf1fe19689cd9fdca11fe9c3eb # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024100117-bundle-qualified-91c8@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

f97cdbbf187f ("serial: qcom-geni: fix false console tx restart") 1788cf6a91d9 ("tty: serial: switch from circ_buf to kfifo") f8fef2fa419f ("tty: msm_serial: use dmaengine_prep_slave_sg()") 9054605ab846 ("tty: 8250_omap: use dmaengine_prep_slave_sg()") 8192fabb0db2 ("tty: 8250_dma: use dmaengine_prep_slave_sg()") 3bcb0bf65c2b ("Merge tag 'tty-6.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty")

thanks,

greg k-h

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

From f97cdbbf187fefcf1fe19689cd9fdca11fe9c3eb Mon Sep 17 00:00:00 2001 From: Johan Hovold johan+linaro@kernel.org Date: Fri, 6 Sep 2024 15:13:30 +0200 Subject: [PATCH] serial: qcom-geni: fix false console tx restart MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

Commit 663abb1a7a7f ("tty: serial: qcom_geni_serial: Fix UART hang") addressed an issue with stalled tx after the console code interrupted the last bytes of a tx command by reenabling the watermark interrupt if there is data in write buffer. This can however break software flow control by re-enabling tx after the user has stopped it.

Address the original issue by not clearing the CMD_DONE flag after polling for command completion. This allows the interrupt handler to start another transfer when the CMD_DONE interrupt has not been disabled due to flow control.

Fixes: c4f528795d1a ("tty: serial: msm_geni_serial: Add serial driver support for GENI based QUP") Fixes: 663abb1a7a7f ("tty: serial: qcom_geni_serial: Fix UART hang") Cc: stable@vger.kernel.org # 4.17 Reviewed-by: Douglas Anderson dianders@chromium.org Tested-by: Nícolas F. R. A. Prado nfraprado@collabora.com Signed-off-by: Johan Hovold johan+linaro@kernel.org Link: https://lore.kernel.org/r/20240906131336.23625-3-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 309c0bddf26a..b88435c0ea50 100644 --- a/drivers/tty/serial/qcom_geni_serial.c +++ b/drivers/tty/serial/qcom_geni_serial.c @@ -306,18 +306,16 @@ static void qcom_geni_serial_setup_tx(struct uart_port *uport, u32 xmit_size) static void qcom_geni_serial_poll_tx_done(struct uart_port *uport) { int done; - u32 irq_clear = M_CMD_DONE_EN;

done = qcom_geni_serial_poll_bit(uport, SE_GENI_M_IRQ_STATUS, M_CMD_DONE_EN, true); if (!done) { writel(M_GENI_CMD_ABORT, uport->membase + SE_GENI_M_CMD_CTRL_REG); - irq_clear |= M_CMD_ABORT_EN; qcom_geni_serial_poll_bit(uport, SE_GENI_M_IRQ_STATUS, M_CMD_ABORT_EN, true); + writel(M_CMD_ABORT_EN, uport->membase + SE_GENI_M_IRQ_CLEAR); } - writel(irq_clear, uport->membase + SE_GENI_M_IRQ_CLEAR); }

static void qcom_geni_serial_abort_rx(struct uart_port *uport) @@ -378,6 +376,7 @@ static void qcom_geni_serial_poll_put_char(struct uart_port *uport, unsigned char c) { writel(DEF_TX_WM, uport->membase + SE_GENI_TX_WATERMARK_REG); + writel(M_CMD_DONE_EN, uport->membase + SE_GENI_M_IRQ_CLEAR); qcom_geni_serial_setup_tx(uport, 1); WARN_ON(!qcom_geni_serial_poll_bit(uport, SE_GENI_M_IRQ_STATUS, M_TX_FIFO_WATERMARK_EN, true)); @@ -422,6 +421,7 @@ __qcom_geni_serial_console_write(struct uart_port *uport, const char *s, }

writel(DEF_TX_WM, uport->membase + SE_GENI_TX_WATERMARK_REG); + writel(M_CMD_DONE_EN, uport->membase + SE_GENI_M_IRQ_CLEAR); qcom_geni_serial_setup_tx(uport, bytes_to_send); for (i = 0; i < count; ) { size_t chars_to_write = 0; @@ -463,7 +463,6 @@ static void qcom_geni_serial_console_write(struct console *co, const char *s, bool locked = true; unsigned long flags; u32 geni_status; - u32 irq_en;

WARN_ON(co->index < 0 || co->index >= GENI_UART_CONS_PORTS);

@@ -495,12 +494,6 @@ static void qcom_geni_serial_console_write(struct console *co, const char *s, * has been sent, in which case we need to look for done first. */ qcom_geni_serial_poll_tx_done(uport); - - if (!kfifo_is_empty(&uport->state->port.xmit_fifo)) { - irq_en = readl(uport->membase + SE_GENI_M_IRQ_EN); - writel(irq_en | M_TX_FIFO_WATERMARK_EN, - uport->membase + SE_GENI_M_IRQ_EN); - } }

__qcom_geni_serial_console_write(uport, s, count);