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

From: Aurelien Jarno <aurelien@aurel32.net>
To: Troy Mitchell <troy.mitchell@linux.spacemit.com>
Cc: Andi Shyti <andi.shyti@kernel.org>, Yixun Lan <dlan@gentoo.org>,
	Alex Elder <elder@riscstar.com>,
	Troy Mitchell <troymitchell988@gmail.com>,
	linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-riscv@lists.infradead.org, spacemit@lists.linux.dev
Subject: Re: [PATCH v2 6/6] i2c: spacemit: introduce pio for k1
Date: Fri, 26 Sep 2025 18:47:14 +0200	[thread overview]
Message-ID: <aNbDkn9AC4FFx-Zc@aurel32.net> (raw)
In-Reply-To: <20250925-k1-i2c-atomic-v2-6-46dc13311cda@linux.spacemit.com>

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@linux.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().

> +			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).

>  	spacemit_i2c_init(i2c);
>  

Regards
Aurelien

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                     http://aurel32.net