| Message ID | 20241001125033.10625-5-johan+linaro@kernel.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | serial: qcom-geni: fix receiver enable | expand |
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
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
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(-)