We are having issues with STM32MP157 UART7 (address 40018000) exiting low power CStop mode and waking up Linux (v4.19 from ST github).
We have confirmed that CStop mode is entered, and it can be exited using an external interrupt (55 pmic_irq), however it does not exit CStop mode with UART7 RX.
The stm32mp175c.dtsi defines uart7 interrupts as GIC interrupt 82 and EXTI interrupt 32, and defines the uart as a wakeup source
uart7: serial@40018000 {
...
interrupt-names = "event", "wakeup";
interrupts-extended = <&intc GIC_SPI 82 IRQ_TYPE_LEVEL_HIGH>,
<&exti 32 1>;
...
wakeup-source;
Here is our DTS entry for uart7 and the pins for default, sleep and idle modes. DMA is also disabled since it was causing issues entering suspend-to-RAM. Using the 'interrupts =' property, we enabled interrupts 82 and 32, matching the dtsi.
uart7_pins_mx: uart7_mx-0 {
pins1 {
pinmux = <STM32_PINMUX('E', 7, AF7)>, /* UART7_RX */
<STM32_PINMUX('E', 10, AF7)>; /* UART7_CTS */
bias-disable;
};
pins2 {
pinmux = <STM32_PINMUX('E', 8, AF7)>, /* UART7_TX */
<STM32_PINMUX('E', 9, AF7)>; /* UART7_RTS */
bias-disable;
drive-push-pull;
slew-rate = <0>;
};
};
uart7_sleep_pins_mx: uart7_sleep_mx-0 {
pins {
pinmux = <STM32_PINMUX('E', 7, ANALOG)>, /* UART7_RX */
<STM32_PINMUX('E', 8, ANALOG)>, /* UART7_TX */
<STM32_PINMUX('E', 9, ANALOG)>, /* UART7_RTS */
<STM32_PINMUX('E', 10, ANALOG)>; /* UART7_CTS */
};
};
uart7_idle_pins_mx: uart7_mx-0 {
pins1 {
pinmux = <STM32_PINMUX('E', 7, AF7)>, /* UART7_RX */
<STM32_PINMUX('E', 10, AF7)>; /* UART7_CTS */
bias-disable;
};
pins2 {
pinmux = <STM32_PINMUX('E', 8, ANALOG)>, /* UART7_TX */
<STM32_PINMUX('E', 9, AF7)>; /* UART7_RTS */
bias-disable;
drive-push-pull;
slew-rate = <0>;
};
};
&uart7{
pinctrl-names = "default", "sleep", "idle";
pinctrl-0 = <&uart7_pins_mx>;
pinctrl-1 = <&uart7_sleep_pins_mx>;
pinctrl-2 = <&uart7_idle_pins_mx>;
/delete-property/dmas;
/delete-property/dma-names;
interrupts = <82>, <32>;
uart-has-rtscts;
st,hw-flow-ctrl;
status = "okay";
};
On boot we see the following log:
[ 0.396996] stm32-usart 40010000.serial: Linked as a consumer to 48000000.dma
[ 0.397419] 40010000.serial: ttySTM0 at MMIO 0x40010000 (irq = 23, base_baud = 4000000) is a stm32-usart
[ 1.200314] console [ttySTM0] enabled
[ 1.205840] stm32-usart 40018000.serial: interrupt mode used for rx (no dma)
[ 1.211528] stm32-usart 40018000.serial: interrupt mode used for tx (no dma)
[ 1.218523] 40018000.serial: ttySTM2 at MMIO 0x40018000 (irq = 30, base_baud = 6527435) is a stm32-usart
Here is what is in the interrupt table:
root@stm32mp157:~ # cat /proc/interrupts |grep serial
23: 372 0 GIC-0 84 Level 40010000.serial
30: 3 0 GIC-0 114 Level 40018000.serial <----- This is only present when the uart port is opened by a program
67: 0 0 stm32-exti-h 30 Edge 40010000.serial:wakeup
68: 0 0 stm32-exti-h 32 Edge 40018000.serial:wakeup
And the wakeup sources are enabled.
root@stm32mp157:~ # find /sys/devices/ -name wakeup | while read f; do echo $f; cat $f; done
...
/sys/devices/platform/soc/40018000.serial/power/wakeup
enabled
/sys/devices/platform/soc/40018000.serial/tty/ttySTM2/power/wakeup
enabled
...
However once we enter suspend-to-RAM, RX on the uart7 does not wake the processor up. We have confirmed that when Linux is awake, data is received correctly, and the reading program works before and after suspend-to-RAM.
How can we enable wakeup on RX?
Thank you
