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); + enable_irq(uport->irq);
return 0; @@ -1264,7 +1269,6 @@ static void qcom_geni_serial_set_termios(struct uart_port *uport, unsigned int avg_bw_core; unsigned long timeout;
- qcom_geni_serial_stop_rx(uport); /* baud rate */ baud = uart_get_baud_rate(uport, termios, old, 300, 4000000);
@@ -1280,7 +1284,7 @@ static void qcom_geni_serial_set_termios(struct uart_port *uport, dev_err(port->se.dev, "Couldn't find suitable clock rate for %u\n", baud * sampling_rate); - goto out_restart_rx; + return; }
dev_dbg(port->se.dev, "desired_rate = %u, clk_rate = %lu, clk_div = %u\n", @@ -1371,8 +1375,6 @@ static void qcom_geni_serial_set_termios(struct uart_port *uport, writel(stop_bit_len, uport->membase + SE_UART_TX_STOP_BIT_LEN); writel(ser_clk_cfg, uport->membase + GENI_SER_M_CLK_CFG); writel(ser_clk_cfg, uport->membase + GENI_SER_S_CLK_CFG); -out_restart_rx: - qcom_geni_serial_start_rx(uport); }
#ifdef CONFIG_SERIAL_QCOM_GENI_CONSOLE
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.
On Thu, Oct 03, 2024 at 01:10:47PM -0700, Doug Anderson wrote:
On Tue, Oct 1, 2024 at 5:51 AM Johan Hovold johan+linaro@kernel.org wrote:
@@ -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.
Heh, yeah, that comment dates back to 2002 and probably wasn't even correct back then.
This function is called with the port mutex held (and interrupts enabled), and I need to take the port lock to serialise against the console code.
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.
Yeah, I tried to find a reason for why things were done this way, but it was probably just copied from the vendor driver. The hardware doesn't seem to require stopping rx in set_termios() (and tx is not stopped anyway), which could otherwise have been a reason.
Johan
linux-stable-mirror@lists.linaro.org
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Johan Hovold