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

-----Original Message-----
From: Fil Dunsky <redacted>
Sent: Wednesday, September 30, 2026 7:25 PM
To: Arnd Bergmann <arnd@arndb.de>
Cc: Linus Walleij <linusw@kernel.org>; Krzysztof Kozlowski <krzk@kernel.org>;
Rob Herring [off-list ref]; Krzysztof Kozlowski [off-list ref];
Conor Dooley [off-list ref]; Greg Kroah-Hartman
[off-list ref]; Jiri Slaby [off-list ref]; Russell King
[off-list ref]; Alexandre Belloni [off-list ref];
Drew Fustini [off-list ref]; Lorenzo Pieralisi [off-list ref];
linux-arm-kernel@lists.infradead.org; devicetree@vger.kernel.org;
linux-kernel@vger.kernel.org; linux-serial@vger.kernel.org; Jason Li
[off-list ref]; Jason Li [off-list ref]
Subject: Re: [PATCH RFC 07/10] tty: serial: Add Cortina Systems CS75xx UART
driver

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On Wed, Sep 30, 2026 at 01:08:07PM +0200, Arnd Bergmann wrote:

quoted

On Wed, Sep 30, 2026, at 12:57, Linus Walleij wrote:

quoted

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-jaso
n.li@cortina-access.com/

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).

quoted

quoted

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

Yes, they are actually same HW logic. But the brand name of CSxxxx is owned by Marvell instead of Cortina-Access now.
Will there any legal issue if unify them as one driver?


Jason