linux-kernel - Re: [PATCH v2 6/6] i2c: spacemit: introduce pio for k1

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Message-ID: <7F98284B9618900A+aNdiTKvvbg4G-LwM@troy-wujie14pro-arch>
Date: Sat, 27 Sep 2025 12:04:28 +0800
From: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
To: Yixun Lan <dlan@...too.org>,
	Troy Mitchell <troy.mitchell@...ux.spacemit.com>
Cc: Andi Shyti <andi.shyti@...nel.org>, Alex Elder <elder@...cstar.com>,
	Troy Mitchell <troymitchell988@...il.com>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org, spacemit@...ts.linux.dev
Subject: Re: [PATCH v2 6/6] i2c: spacemit: introduce pio for k1

On Sat, Sep 27, 2025 at 09:45:47AM +0800, Yixun Lan wrote:
> Hi Troy,
> 
> On 10:02 Thu 25 Sep     , Troy Mitchell wrote:
> > This patch introduces I2C PIO functionality for the Spacemit K1 SoC,
> > enabling the use of I2C with interrupts disabled.
> I feel it's more proper to say
> s/with interrupts disabled/in atomic context/
Good point.

> 
> I've noticed that K1 I2C controller support three different transmission mode:
>  non-fifo, fifo mode, dma mode
> 
> while you are trying to implement pio support, I'd suggest to think one
> further step in the long run - support more fifo/dma + normal/atomic features,
I understand your concern, but I have reviewed the code structure,
and adding FIFO support would not significantly affect the current PIO implementation.

> 
> Personally, I'd like to see fifo mode implemented before adding pio
> support, as it will bring quite significant code changes, require heavy
> code review effort. And yes, this will put more demanding work on your side
> and may slow things a bit..
That said, we don’t have any plans to support FIFO at this point,
and PIO functionality is something we need urgently.
So I will continue to push this patch (tomorrow).
Thanks for your understanding. For details on the code changes, please see above.

In addition, if anyone is interested in adding FIFO support, I’d be happy to help.

                                            - Troy
>
> 
> -- 
> Yixun Lan (dlan)
>