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

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Message-ID: <64AD69A1C43D8A13+aNe7RUmS73q-jSBk@troy-wujie14pro-arch>
Date: Sat, 27 Sep 2025 18:24:05 +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 06:16:48PM +0800, Yixun Lan wrote:
> Hi Troy,
> 
> On 12:04 Sat 27 Sep     , Troy Mitchell wrote:
> > 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.
> we will see..
> 
> > 
> > > 
> > > 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).
> please do not flush the mailing list and give people some time, I haven't seen 
> enough reviews coming, please wait for ~one week before sending next version,
> or make sure you've accumulated enough changes..
Okay.. I will wait for more review

> 
> > 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.
> > 
> do you want to push the work (support fifo mode) to community?
Personally, I want.
Since K3 is going to reuse the upstream driver,
PIO support has high priority (needed as P1, e.g. for shutdown and reboot).
FIFO support, is not considered a high priority at this point.

That's why I want to push PIO ASAP
Does this make sense?

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