Re: [PATCH RFC 07/10] tty: serial: Add Cortina Systems CS75xx UART driver

[Fil Dunsky]

On Wed, Sep 30, 2026 at 01:08:07PM +0200, Arnd Bergmann wrote:
> On Wed, Sep 30, 2026, at 12:57, Linus Walleij wrote:
>> Look at this in your Linux tree:
>> git log -p b61c8bf4694b5115766849378dcb8787ff54e65e
>>
>> This is essentially a resurrection of that driver.
>
> Jason actually came back this summer to try again, see
> https://lore.kernel.org/linux-arm-kernel/20260610112821.3030099-1-jason.li@xxxxxxxxxxxxxxxxxx/

Thanks, I was not aware of either. Comparing the two, it is the same
IP: the offsets of CFG, RX_SAMPLE, TX_DAT, RX_DAT, INFO, IE and INT
and the bit layout of CFG, INFO and the interrupt registers are
identical. The Cortina Access version additionally has a flow control
register at 0x04, RT_TUNE at 0x0c, STATUS at 0x2c and three more
interrupt causes (break, RX underrun, TX overrun).

>> Anyways, clearly this driver is not just for CS75xx so name it
>> cortina-uart.c simply, and update symbols accordingly. Kconfig
>> should be SERIAL_CORTINA etc.
>
> I think we clearly want a driver that works for both the Cortina
> Systems CS75xx and the Cortina Access CA82xx, hopefully that
> would also support the ones inbetween (CS80xx, CA81xx).

Agreed. For v2 I will rename it to drivers/tty/serial/cortina-uart.c
with SERIAL_CORTINA and SERIAL_CORTINA_CONSOLE, and name the binding
so that it can take the other parts. I would keep SoC specific
compatibles ("cortina,cs7542-uart", later e.g.
"cortina-access,ca8289-uart"), so that the flow control and the extra
interrupt causes can be enabled per compatible.

I can only test on the CS7542. Jason, would you be fine with adding
the CA82xx on top of this driver instead of a separate one? I am happy
to add the compatible and the bits you need if you can test them.

Thanks,
Fil