Hi,
On Tue, Oct 1, 2024 at 5:51 AM Johan Hovold johan+linaro@kernel.org wrote:
The receiver should be enabled in the startup() callback and there is no need to stop it on every termios update.
Since commit 6f3c3cafb115 ("serial: qcom-geni: disable interrupts during console writes") the calls to manipulate the secondary interrupts, which were done without holding the port lock, can lead to the receiver being left disabled when set_termios() races with the console code (e.g. when init opens the tty during boot).
The calls to stop and start rx in set_termios() can similarly race with DMA completion and, for example, cause the DMA buffer to be unmapped twice or the mapping to be leaked.
Fixes: 6f3c3cafb115 ("serial: qcom-geni: disable interrupts during console writes") Fixes: 2aaa43c70778 ("tty: serial: qcom-geni-serial: add support for serial engine DMA") Fixes: c4f528795d1a ("tty: serial: msm_geni_serial: Add serial driver support for GENI based QUP") Cc: stable@vger.kernel.org # 6.3 Cc: Bartosz Golaszewski bartosz.golaszewski@linaro.org Signed-off-by: Johan Hovold johan+linaro@kernel.org
drivers/tty/serial/qcom_geni_serial.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c index dea688db0d7c..5b6c5388efee 100644 --- a/drivers/tty/serial/qcom_geni_serial.c +++ b/drivers/tty/serial/qcom_geni_serial.c @@ -1179,6 +1179,11 @@ static int qcom_geni_serial_startup(struct uart_port *uport) if (ret) return ret; }
uart_port_lock_irq(uport);qcom_geni_serial_start_rx(uport);uart_port_unlock_irq(uport);
I _think_ you don't need the locking here. The documentation for the "startup" callback say:
* Interrupts: globally disabled.
Other than that, this looks reasonable to me. I seem to recall previous discussions where _someone_ was relying on the qcom_geni_serial_start_rx() at the end of termios for some reason (which always felt like a bad design), but I can't find those old discussions. I suspect that the fact that you've added the start_rx in startup() is what we needed.