STM32MP157C Enabling usart1 by using device tree

[mertt]

Hi all,

The development board we are using STM32MP157C-YA157C from Myirtech is running Ubuntu 18 with openstlinux.

I am trying to interface the usart1 with another module but by default, the peripheral is not enabled from device tree.

So, I modified the device tree as follows (pins z6 and z7 are used by usart1) according to the document of ST :

usart1_pins_a: usart1-0 {
pins1 {
pinmux = <STM32_PINMUX('Z', 7, AF7)>; /* UART1_TX */
bias-disable;
drive-push-pull;
slew-rate = <0>;
};
pins2 {
pinmux = <STM32_PINMUX('Z', 6, AF7)>; /* UART1_RX */
bias-disable;
};
};

usart1_idle_pins_a: usart1-idle-0 {
pins1 {
pinmux = <STM32_PINMUX('Z', 7, ANALOG)>; /* UART1_TX */
};
pins2 {
pinmux = <STM32_PINMUX('Z', 6, AF7)>; /* UART1_RX */
bias-disable;
};
};

usart1_sleep_pins_a: usart1-sleep-0 {
pins {
pinmux = <STM32_PINMUX('Z', 7, ANALOG)>, /* UART1_TX */
<STM32_PINMUX('Z', 6, ANALOG)>; /* UART1_RX */
};
};

&usart1 {
	pinctrl-names = "default", "sleep", "idle";	/* pin configurations definition */
	pinctrl-0 = <&usart1_pins_a>;			/* default pin configuration selection */
	pinctrl-1 = <&usart1_sleep_pins_a>;		/* sleep pin configuration selection */
	pinctrl-2 = <&usart1_idle_pins_a>;		/* idle pin configuration selection */
	status = "okay";				/* device activation */
};

aliases {
		ethernet0 = &ethernet0;
		serial0 = &uart4;
		serial1 = &usart1;
		serial2 = &uart8;//rs232
		serial3 = &uart5;//rs485
		serial4 = &uart7;//bt
	};

usart1: serial@5c000000 {
			compatible = "st,stm32h7-uart";
			reg = <0x5c000000 0x400>;
			interrupts-extended = <&exti 26 IRQ_TYPE_LEVEL_HIGH>;
			//clocks = <&scmi0_clk CK_SCMI0_USART1>;
			//resets = <&scmi0_reset RST_SCMI0_USART1>;
			clocks = <&rcc USART1_K>;
			resets = <&rcc USART1_R>;
			
			wakeup-source;
			power-domains = <&pd_core>;
			status = "disabled";
		};

On boot up, the kernel cannot enable the usart1 module (5c000000):

[ 1.961813] stm32-usart 40010000.serial: interrupt mode for rx (no dma)
[ 1.961838] stm32-usart 40010000.serial: interrupt mode for tx (no dma)
[ 1.961877] 40010000.serial: ttySTM0 at MMIO 0x40010000 (irq = 57, base_baud = 4000000) is a stm32-usart
[ 3.239179] 40011000.serial: ttySTM3 at MMIO 0x40011000 (irq = 58, base_baud = 4000000) is a stm32-usart
[ 3.249682] 40018000.serial: ttySTM4 at MMIO 0x40018000 (irq = 59, base_baud = 4000000) is a stm32-usart
[ 3.264333] 40019000.serial: ttySTM2 at MMIO 0x40019000 (irq = 60, base_baud = 4000000) is a stm32-usart
[ 3.279710] stm32-usart: probe of 5c000000.serial failed with error -22

 The clock summary is as follows (grep -E "clock|usart" /sys/kernel/debug/clk/clk_summary | sed 's,\s\+, ,g' | column -t):

clock     count  count  count  rate       accuracy  phase  cycle
usart1_k  0      0      0      64000000   0         0      50000
usart3_k  0      0      0      64000000   0         0      50000
usart2_k  0      0      0      64000000   0         0      50000
usart6    0      0      0      104438965  0         0      50000
usart3    0      0      0      104438965  0         0      50000
usart2    0      0      0      104438965  0         0      50000

I noticed that the usart1_k  clock is not enabled. How can I enable it?
What am I missing?

Thank you.

Best regards,

Mert

[Olivier GALLIEN · Accepted solution]

Hi @mertt 

I think it miss to enable  and provide a source clock to UART1 clock in Tf-a Device Tree 

st,pkcs = <
...
CLK_UART1_DISABLED

CLK_UART1_HSI
...
>;

Olivier 

In order to give better visibility on the answered topics, please click on 'Accept as Solution' on the reply which solved your issue or answered your question.

[mertt]

Hi @Olivier GALLIEN 

Thank you for the answer.

In the file include/dt-bindings/clock/stm32mp1-clks.h, there are the following definitions:

#define USART1 64
...
#define CK_SCMI0_HSI 1
...
#define CK_SCMI0_USART1 20

I suspect that the kernel versions are different.

Under the rcc: rcc@50000000, I can use the following, if it is correct:

st,pkcs = <
...
CK_SCMI0_USART1
...
>;

Best regards,
Mert

[mertt]

> I think it miss to enable  and provide a source clock to UART1 clock in Tf-a Device Tree 

I missed the tf-a part, I will try to compile and change the boot partition again.

Best regards.

[Olivier GALLIEN]

Hi @mertt 

If you are using op-tee you may also have a look to Op-tee DT. 

Olivier 

[mertt]

It worked, thanks.

[3.270418] 5c000000.serial: ttySTM1 at MMIO 0x5c000000 (irq = 61, base_baud = 4000000) is a stm32-usart