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

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Message-ID: <4AE256D88658986A+aNjQf1whw2K1t6JC@kernel.org>
Date: Sun, 28 Sep 2025 14:06:55 +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 Fri, Sep 26, 2025 at 07:10:55PM +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.
> > 
> > Signed-off-by: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
> > ---
> >  drivers/i2c/busses/i2c-k1.c | 164 +++++++++++++++++++++++++++++++++++++-------
> >  1 file changed, 140 insertions(+), 24 deletions(-)
> > 
> > diff --git a/drivers/i2c/busses/i2c-k1.c b/drivers/i2c/busses/i2c-k1.c
> > index 6b918770e612e098b8ad17418f420d87c94df166..e403eb7d6f329f4fe5c5242f94cc21094dff105c 100644
> > --- a/drivers/i2c/busses/i2c-k1.c
> > +++ b/drivers/i2c/busses/i2c-k1.c
> > @@ -97,6 +97,9 @@
> >  
> >  #define SPACEMIT_BUS_RESET_CLK_CNT_MAX		9
> >  
> > +/* Constants */
> > +#define SPACEMIT_WAIT_TIMEOUT      1000 /* ms */
> > +
> >  enum spacemit_i2c_state {
> >  	SPACEMIT_STATE_IDLE,
> >  	SPACEMIT_STATE_START,
> > @@ -125,6 +128,7 @@ struct spacemit_i2c_dev {
> >  
> >  	enum spacemit_i2c_state state;
> >  	bool read;
> > +	bool is_pio;
> using_pio_mode or simply use_pio, but have to say..
> 
> I feel it's improper to have this flag here, since it's not a controller
> level feature, I understand it was introduced to support aotmic operation
> 
> Personally, I'd suggest to pass the flag in xfer(), then propagate down to
> whatever needed, so it limit to single transmission which more flexible
I no longer agree with moving the flag into xfer.
Keeping it as a global variable is better,
otherwise it would affect several functions:
wait_bus_idle(), start(), init(), handle_write(), handle_read(), etc.

                - Troy