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

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Message-ID: <F3CBA41FF1849DD5+aNdint66DRw4AcZK@troy-wujie14pro-arch>
Date: Sat, 27 Sep 2025 12:05:50 +0800
From: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
To: Troy Mitchell <troy.mitchell@...ux.spacemit.com>,
	Andi Shyti <andi.shyti@...nel.org>, Yixun Lan <dlan@...too.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 06:47:14PM +0200, Aurelien Jarno wrote:
> Hi Troy,
> 
> On 2025-09-25 10:02, 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
> 
> [snip]
> 
> > @@ -293,10 +307,54 @@ static void spacemit_i2c_start(struct spacemit_i2c_dev *i2c)
> >  	/* send start pulse */
> >  	val = readl(i2c->base + SPACEMIT_ICR);
> >  	val &= ~SPACEMIT_CR_STOP;
> > -	val |= SPACEMIT_CR_START | SPACEMIT_CR_TB | SPACEMIT_CR_DTEIE;
> > +	val |= SPACEMIT_CR_START | SPACEMIT_CR_TB;
> > +
> > +	if (!i2c->is_pio)
> > +		val |= SPACEMIT_CR_DTEIE;
> > +
> >  	writel(val, i2c->base + SPACEMIT_ICR);
> >  }
> >  
> > +static irqreturn_t spacemit_i2c_irq_handler(int irq, void *devid);
> > +static int spacemit_i2c_wait_pio_xfer(struct spacemit_i2c_dev *i2c)
> > +{
> > +	u32 msec = jiffies_to_msecs(i2c->adapt.timeout);
> > +	ktime_t timeout = ktime_add_ms(ktime_get(), msec);
> > +	int ret;
> > +
> > +	while (i2c->unprocessed && ktime_compare(ktime_get(), timeout) < 0) {
> > +		udelay(10);
> > +		i2c->status = readl(i2c->base + SPACEMIT_ISR);
> > +
> > +		spacemit_i2c_clear_int_status(i2c, i2c->status);
> > +
> > +		if (!(i2c->status & SPACEMIT_SR_IRF) && !(i2c->status & SPACEMIT_SR_ITE))
> > +			continue;
> > +
> > +		spacemit_i2c_irq_handler(0, i2c);
> > +
> > +		i2c->status = readl(i2c->base + SPACEMIT_ISR);
> > +
> > +		/*
> > +		 * This is the last byte to write of the current message.
> > +		 * If we do not wait here, control will proceed directly to start(),
> > +		 * which would overwrite the current data.
> > +		 */
> > +		if (!i2c->read && !i2c->unprocessed) {
> > +			ret = readl_poll_timeout(i2c->base + SPACEMIT_ISR,
> > +						i2c->status, i2c->status & SPACEMIT_SR_ITE,
> > +						30, 1000);
> 
> This needs to be readl_poll_timeout_atomic(), like you changed in 
> spacemit_i2c_wait_bus_idle().
Yes, nice catch!
That's my mistake... I forgot this.
> 
> > +			if (ret)
> > +				return 0;
> > +		}
> > +	}
> > +
> > +	if (i2c->unprocessed)
> > +		return 0;
> > +
> > +	return 1;
> > +}
> > +
> >  static int spacemit_i2c_xfer_msg(struct spacemit_i2c_dev *i2c)
> >  {
> >  	unsigned long time_left;
> 
> [snip]
> 
> > @@ -479,15 +578,21 @@ static void spacemit_i2c_calc_timeout(struct spacemit_i2c_dev *i2c)
> >  	i2c->adapt.timeout = usecs_to_jiffies(timeout + USEC_PER_SEC / 10) / i2c->msg_num;
> >  }
> >  
> > -static int spacemit_i2c_xfer(struct i2c_adapter *adapt, struct i2c_msg *msgs, int num)
> > +static inline int
> > +spacemit_i2c_xfer(struct i2c_adapter *adapt, struct i2c_msg *msgs, int num, bool is_pio)
> >  {
> >  	struct spacemit_i2c_dev *i2c = i2c_get_adapdata(adapt);
> >  	int ret;
> >  
> > +	i2c->is_pio = is_pio;
> > +
> >  	i2c->msgs = msgs;
> >  	i2c->msg_num = num;
> >  
> > -	spacemit_i2c_calc_timeout(i2c);
> > +	if (!i2c->is_pio)
> > +		spacemit_i2c_calc_timeout(i2c);
> > +	else
> > +		i2c->adapt.timeout = SPACEMIT_WAIT_TIMEOUT;
> 
> Thanks for fixing that, however i2c->adapt.timeout needs to be in 
> jiffies, so you want to use msecs_to_jiffies(SPACEMIT_WAIT_TIMEOUT).
Thanks for pointing this out!

                - Troy
> 
> >  	spacemit_i2c_init(i2c);
> >  
> 
> Regards
> Aurelien
> 
> -- 
> Aurelien Jarno                          GPG: 4096R/1DDD8C9B
> aurelien@...el32.net                     http://aurel32.net
>