RS485 stop working

[kzoltaan]

This is my RS485 config on boneblack.

`&am33xx_pinmux {
uart1_pins: uart1_pins {
pinctrl-single,pins = <
0x178 (PIN_OUTPUT | MUX_MODE7) /* uart1_ctsn.uart1_ctsn /
0x17c (PIN_OUTPUT_PULLDOWN | MUX_MODE7) / uart1_rtsn.uart1_rtsn /
0x180 (PIN_INPUT_PULLUP | MUX_MODE0) / uart1_rxd.uart1_rxd /
0x184 (PIN_OUTPUT | MUX_MODE0) / uart1_txd.uart1_txd */
>;
};

};

&ocp{
P9_19_pinmux {
status = "disabled";
};

    P9_20_pinmux{
            status = "disabled";
    };

    P9_24_pinmux{
            status = "disabled";
    };


    P9_26_pinmux {
            status = "disabled";
    };

};

&uart1 {
pinctrl-names = "default";
pinctrl-0 = <&uart1_pins>;
status = "okay";
rts-gpio = <&gpio0 13 GPIO_ACTIVE_HIGH>;
rs485-rts-active-high;
rs485-rx-during-tx;
rs485-rts-delay = <1 1>;
linux,rs485-enabled-at-boot-time;
};
`

This is working on 4.2.5-armv7-x2 but not working on 4.9.0-armv7-x3. RTS pin is not working. Receive is OK. What is wrong?

[kinkazu]

does
rts-gpios = <&gpio0 13 GPIO_ACTIVE_HIGH>;
make a difference?

[kzoltaan]

I tried it! And no. Beacause: I think this is OMAP serial, and
https://github.com/torvalds/linux/blob/master/drivers/tty/serial/omap-serial.c
at line 1623
up->rts_gpio = of_get_named_gpio_flags(np, "rts-gpio", 0, &flags);

[kinkazu]

I am on 4.9.15-bone4 and have got 8250

[kzoltaan]

it is working on 4.9.15-bone4? what is 8250?
not works on 4.10.1-armv7-x1 :(

[kzoltaan]

Oh YES! S1 is rs485
[ 0.009123] WARNING: Your 'console=ttyO0' has been replaced by 'ttyS0' [ 2.182018] 44e09000.serial: ttyS0 at MMIO 0x44e09000 (irq = 158, base_baud = 3000000) is a 8250 [ 2.194875] console [ttyS0] enabled [ 2.195884] 48022000.serial: ttyS1 at MMIO 0x48022000 (irq = 159, base_baud = 3000000) is a 8250 [ 2.196708] 48024000.serial: ttyS2 at MMIO 0x48024000 (irq = 160, base_baud = 3000000) is a 8250 [ 2.197488] 481a6000.serial: ttyS3 at MMIO 0x481a6000 (irq = 161, base_baud = 3000000) is a 8250

[kzoltaan]

This is the problem. 8250 IS NOT SUPPORT RTS GPIO. but fixme. previous was OMAP UART

[kinkazu]

Would be nice to have rts gpio working on 8250 and dts shared, I don't know why this is not important for 8250 developers.

[RobertCNelson]

Switch to the non generic omap serial driver. There was one developer working on it for the generic 8250 driver, but he seems to have disappeared.

Regards,

[kzoltaan]

Here is the modification for rs485 by driver author.
http://lists.infradead.org/pipermail/linux-arm-kernel/2014-July/271071.html

8250 driver also refer to omap3-uart, so when I change the driver in the device tree, there is no effect.
https://github.com/RobertCNelson/linux-stable-rcn-ee/blob/4.10-armv7-x1/drivers/tty/serial/8250/8250_omap.c#L1082

How can I switch the driver without rebuild the kernel? Can I do this?

[ercint]

Hi @kzoltaan ,

did you find a way to do that?

Thanks in advance

[kzoltaan]

I have an idea. I tried out and the RTS is working with user led.
I made a copy from https://github.com/RobertCNelson/linux-stable-rcn-ee/blob/4.9.9-ti-rt-r22/drivers/tty/serial/omap-serial.c ( i use 4.9.9-ti kernel right now)
I rewrite the ids

static const struct of_device_id omap_serial_of_match[] = {
        { .compatible = "ti,omap-uart-rs485" },
        {},
};

--- use it for uart1 ---

 uart1: serial@48022000 {
                        compatible = "ti,omap-uart-rs485";
                        ti,hwmods = "uart2";
                        clock-frequency = <48000000>;
                        reg = <0x48022000 0x2000>;
                        interrupts = <73>;
                        status = "disabled";
                        dmas = <&edma 28 0>, <&edma 29 0>;
                        dma-names = "tx", "rx";
                };

I build the module:

Makefile:
obj-m += omap-serial.o

all:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

run make, copy the ko into drivers/tty/serial and run depmod

dtsi:

&uart1 {
        pinctrl-names = "default";
        pinctrl-0 = <&uart1_pins>;
        status = "okay";
        rts-gpio = <&gpio1 24 GPIO_ACTIVE_HIGH>; // now this is user led
        rs485-rts-active-high;
        rs485-rx-during-tx;
        rs485-rts-delay = <10 0>;
        linux,rs485-enabled-at-boot-time;
};

build your device tree and try it. I'm using rs232 this is with 8250 and looks good.

[    2.397068] 44e09000.serial: ttyS0 at MMIO 0x44e09000 (irq = 158, base_baud = 3000000) is a 8250
[    2.411349] 48024000.serial: ttyS2 at MMIO 0x48024000 (irq = 160, base_baud = 3000000) is a 8250
[   19.639940] 48022000.serial: ttyO1 at MMIO 0x48022000 (irq = 159, base_baud = 3000000) is a OMAP UART1

please confirm!

[Ib2cool]

I have without success tried the get RS485 with RTS to drive DE and /RE.
I'm using kernel 4.9.88 and BB-UART4-RS485-00A0.dtbo
I have verified that I can toggle P9_27 as GPIO, but nothing happens when UART4 transmits
I tried with the default 8250 driver and I have also compiled the OMAP-SERIAL
A lot of the overlays handling have been changed and I have lost the overview.
Can someone provide a guide to get RS485 with RTS working?

[kzoltaan]

my solution is working