SC16is752 I2C bus

didiernortek · December 13, 2023, 4:49pm

Hi,
I’m trying to get working a 2 channel RS232 HAT ( so natively made for RPi), based on SC16is752 chip.
I’ve activated i2c-b overlay and I can see the device at expected i2c address ( 0x4c).
But now I’m a little bit confused about what I have to do because I don’t see any I2C uart device under /dev .
Do I need a driver ? Should I recompile all the kernel with a specific option or may be only a module ?

So advice are welcome !

librecomputer · December 21, 2023, 7:34am

We have enabled the module (driver) for SC16IS752 in the latest kernel update. You need to create a device tree that binds the hardware with the driver using libretech-wiring-tool. Please see other SPI overlays as examples. Feel free to submit a pull request once you have created and tested the overlay with that device.

You mentioned that the device is I2C which should be an error as this IC seems to be a SPI device.

Driver:

github.com

libre-computer-project/libretech-linux/blob/eb365d1ffcea507a6608198f163b41fc726b36b3/drivers/tty/serial/sc16is7xx.c#L461


      
          	.nr_gpio	= 0,
          	.nr_uart	= 1,
          };
          
          static const struct sc16is7xx_devtype sc16is750_devtype = {
          	.name		= "SC16IS750",
          	.nr_gpio	= 8,
          	.nr_uart	= 1,
          };
          
          static const struct sc16is7xx_devtype sc16is752_devtype = {
          	.name		= "SC16IS752",
          	.nr_gpio	= 8,
          	.nr_uart	= 2,
          };
          
          static const struct sc16is7xx_devtype sc16is760_devtype = {
          	.name		= "SC16IS760",
          	.nr_gpio	= 8,
          	.nr_uart	= 1,
          };

Binding:

github.com

libre-computer-project/libretech-linux/blob/eb365d1ffcea507a6608198f163b41fc726b36b3/Documentation/devicetree/bindings/serial/nxp,sc16is7xx.txt#L68


      
          		nxp,modem-control-line-ports = <0 1>; /* Ports 0 and 1 as modem control lines */
          	};
          
          * spi as bus
          
          Required properties:
          - compatible: Should be one of the following:
            - "nxp,sc16is740" for NXP SC16IS740,
            - "nxp,sc16is741" for NXP SC16IS741,
            - "nxp,sc16is750" for NXP SC16IS750,
            - "nxp,sc16is752" for NXP SC16IS752,
            - "nxp,sc16is760" for NXP SC16IS760,
            - "nxp,sc16is762" for NXP SC16IS762.
          - reg: SPI chip select number.
          - interrupts: Specifies the interrupt source of the parent interrupt
            controller. The format of the interrupt specifier depends on the
            parent interrupt controller.
          - clocks: phandle to the IC source clock.
          
          Optional properties:
          - gpio-controller: Marks the device node as a GPIO controller.