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

Aurelien Jarno
2025-09-26T16:47:26Z

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