Trouble setting low_latency mode on /dev/ttyTHS1

We are connecting a device to the /dev/ttyTHS1 serial port that requires us to set low_latency mode to true. On other platforms, we have achieved this with setserial /dev/ttyS0 low_latency (and indeed, this command succeeds on the Jetson Nano’s /dev/ttyS0 port), but when I try this on either of the THS ports, I get the error: “Cannot set serial info: Invalid argument”.

Does the driver for the THS ports support low_latency mode?

From dmesg, the info for this port is:
[ 1.606989] 70006040.serial: ttyTHS1 at MMIO 0x70006040 (irq = 64, base_baud = 0) is a TEGRA_UART

hello ryankerwin,

no, it doesn’t.
may I know what’s your actual use-case.

An added note: The device special file in “/dev” depends on the driver. The special commands (IOCTL calls) available depends on the driver itself (and this is what the serial UART setup commands are…IOCTL calls going to the driver). It is possible that both “/dev/ttyS1” and “/dev/ttyTHS1” exist, and both would be the same UART (note both have a “1”), but different drivers (you’d want to avoid using two different drivers simultaneously, although both can exist at the same time…the availability of the two drivers depends on the device tree “compatible” content for the particular UART).

If you don’t have the “/dev/ttyS1” file to call instead of the “/dev/ttyTHS1” file, then you can only use values supported by the ttyTHS driver. You could use the device tree to add the legacy driver if ttyS1 is missing, but I suspect that with the “low_latency” option it probably would not help, though you could try. Possibly there are also issues with the legacy driver and low_latency, I wouldn’t expect this to have any testing on arm64 and that particular UART.

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