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

[Jason Li]

> -----Original Message-----
> From: Fil Dunsky <filipp.dunsky at gmail.com>
> Sent: Wednesday, September 30, 2026 7:25 PM
> To: Arnd Bergmann <arnd at arndb.de>
> Cc: Linus Walleij <linusw at kernel.org>; Krzysztof Kozlowski <krzk at kernel.org>;
> Rob Herring <robh at kernel.org>; Krzysztof Kozlowski <krzk+dt at kernel.org>;
> Conor Dooley <conor+dt at kernel.org>; Greg Kroah-Hartman
> <gregkh at linuxfoundation.org>; Jiri Slaby <jirislaby at kernel.org>; Russell King
> <linux at armlinux.org.uk>; Alexandre Belloni <alexandre.belloni at bootlin.com>;
> Drew Fustini <fustini at kernel.org>; Lorenzo Pieralisi <lpieralisi at kernel.org>;
> linux-arm-kernel at lists.infradead.org; devicetree at vger.kernel.org;
> linux-kernel at vger.kernel.org; linux-serial at vger.kernel.org; Jason Li
> <jason.li at cortina-access.com>; Jason Li <jason.li at cortina-access.com>
> 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:
> > 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-jaso
> > n.li at 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).
> 
> >> 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