Currently, imx uart defaults to enabling the wake related registers for
all uart devices. However, it is unnecessary for those devices not
configured as wakeup source, so add device_may_wakeup() check before
configuring the uart wake related registers.
Fixes: db1a9b55004c ("tty: serial: imx: Allow UART to be a source for wakeup")
Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
---
drivers/tty/serial/imx.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 500dfc009d03..4ddfc89816bf 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2697,7 +2697,22 @@ static void imx_uart_save_context(struct imx_port *sport)
/* called with irq off */
static void imx_uart_enable_wakeup(struct imx_port *sport, bool on)
{
+ struct tty_port *port = &sport->port.state->port;
+ struct tty_struct *tty;
+ struct device *tty_dev;
u32 ucr3;
+ bool may_wake;
+
+ tty = tty_port_tty_get(port);
+ if (tty) {
+ tty_dev = tty->dev;
+ may_wake = tty_dev && device_may_wakeup(tty_dev);
+ tty_kref_put(tty);
+ }
+
+ /* only configure the wake register when device set as wakeup source */
+ if (!may_wake)
+ return;
uart_port_lock_irq(&sport->port);
--
2.34.1Hi Sherry,
kernel test robot noticed the following build warnings:
[auto build test WARNING on shawnguo/for-next]
[also build test WARNING on tty/tty-testing tty/tty-next tty/tty-linus usb/usb-testing usb/usb-next usb/usb-linus linus/master v6.17-rc7 next-20250922]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Sherry-Sun/tty-serial-imx-Only-configure-the-wake-register-when-device-is-set-as-wakeup-source/20250923-111951
base: https://git.kernel.org/pub/scm/linux/kernel/git/shawnguo/linux.git for-next
patch link: https://lore.kernel.org/r/20250923031613.2448073-2-sherry.sun%40nxp.com
patch subject: [PATCH 1/2] tty: serial: imx: Only configure the wake register when device is set as wakeup source
config: arm-randconfig-004-20250923 (https://download.01.org/0day-ci/archive/20250924/202509240009.Q4htWwxE-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project cafc064fc7a96b3979a023ddae1da2b499d6c954)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250924/202509240009.Q4htWwxE-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202509240009.Q4htWwxE-lkp@intel.com/
All warnings (new ones prefixed by >>):
>> drivers/tty/serial/imx.c:2707:6: warning: variable 'may_wake' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
2707 | if (tty) {
| ^~~
drivers/tty/serial/imx.c:2714:7: note: uninitialized use occurs here
2714 | if (!may_wake)
| ^~~~~~~~
drivers/tty/serial/imx.c:2707:2: note: remove the 'if' if its condition is always true
2707 | if (tty) {
| ^~~~~~~~
drivers/tty/serial/imx.c:2704:15: note: initialize the variable 'may_wake' to silence this warning
2704 | bool may_wake;
| ^
| = 0
1 warning generated.
vim +2707 drivers/tty/serial/imx.c
2696
2697 /* called with irq off */
2698 static void imx_uart_enable_wakeup(struct imx_port *sport, bool on)
2699 {
2700 struct tty_port *port = &sport->port.state->port;
2701 struct tty_struct *tty;
2702 struct device *tty_dev;
2703 u32 ucr3;
2704 bool may_wake;
2705
2706 tty = tty_port_tty_get(port);
> 2707 if (tty) {
2708 tty_dev = tty->dev;
2709 may_wake = tty_dev && device_may_wakeup(tty_dev);
2710 tty_kref_put(tty);
2711 }
2712
2713 /* only configure the wake register when device set as wakeup source */
2714 if (!may_wake)
2715 return;
2716
2717 uart_port_lock_irq(&sport->port);
2718
2719 ucr3 = imx_uart_readl(sport, UCR3);
2720 if (on) {
2721 imx_uart_writel(sport, USR1_AWAKE, USR1);
2722 ucr3 |= UCR3_AWAKEN;
2723 } else {
2724 ucr3 &= ~UCR3_AWAKEN;
2725 }
2726 imx_uart_writel(sport, ucr3, UCR3);
2727
2728 if (sport->have_rtscts) {
2729 u32 ucr1 = imx_uart_readl(sport, UCR1);
2730 if (on) {
2731 imx_uart_writel(sport, USR1_RTSD, USR1);
2732 ucr1 |= UCR1_RTSDEN;
2733 } else {
2734 ucr1 &= ~UCR1_RTSDEN;
2735 }
2736 imx_uart_writel(sport, ucr1, UCR1);
2737 }
2738
2739 uart_port_unlock_irq(&sport->port);
2740 }
2741
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
On Tue, Sep 23, 2025 at 11:16:12AM +0800, Sherry Sun wrote:
>Currently, imx uart defaults to enabling the wake related registers for
>all uart devices. However, it is unnecessary for those devices not
>configured as wakeup source, so add device_may_wakeup() check before
>configuring the uart wake related registers.
I would rewrite as this:
Currently, the i.MX UART driver enables wake-related registers for all UART
devices by default. However, this is unnecessary for devices that are not
configured as wakeup sources. To address this, add a device_may_wakeup()
check before configuring the UART wake-related registers.
>
>Fixes: db1a9b55004c ("tty: serial: imx: Allow UART to be a source for wakeup")
>Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
>---
> drivers/tty/serial/imx.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
>diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
>index 500dfc009d03..4ddfc89816bf 100644
>--- a/drivers/tty/serial/imx.c
>+++ b/drivers/tty/serial/imx.c
>@@ -2697,7 +2697,22 @@ static void imx_uart_save_context(struct imx_port *sport)
> /* called with irq off */
> static void imx_uart_enable_wakeup(struct imx_port *sport, bool on)
> {
>+ struct tty_port *port = &sport->port.state->port;
>+ struct tty_struct *tty;
>+ struct device *tty_dev;
> u32 ucr3;
>+ bool may_wake;
'bool may_wake = false;' otherwise there might be report on using an
uninitalized value by coverity or other tools.
>+
>+ tty = tty_port_tty_get(port);
>+ if (tty) {
>+ tty_dev = tty->dev;
>+ may_wake = tty_dev && device_may_wakeup(tty_dev);
>+ tty_kref_put(tty);
>+ }
>+
>+ /* only configure the wake register when device set as wakeup source */
>+ if (!may_wake)
>+ return;
Regards,
Peng
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