linux-kernel - Re: [PATCH v3] i2c: spacemit: introduce pio for k1

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Message-ID: <A6E9D3643EC66124+aNpORZx6yq8VOfd8@kernel.org>
Date: Mon, 29 Sep 2025 17:15:49 +0800
From: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
To: Andi Shyti <andi.shyti@...nel.org>, Yixun Lan <dlan@...too.org>,
	Alex Elder <elder@...cstar.com>,
	Troy Mitchell <troymitchell988@...il.com>
Cc: linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org, spacemit@...ts.linux.dev,
	Troy Mitchell <troy.mitchell@...ux.spacemit.com>
Subject: Re: [PATCH v3] i2c: spacemit: introduce pio for k1

On Mon, Sep 29, 2025 at 02:07:49PM +0800, Troy Mitchell wrote:
> This patch introduces I2C PIO functionality for the Spacemit K1 SoC,
> enabling the use of I2C in atomic context.
> 
> Signed-off-by: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
> ---
> Changes in v3:
> - drop 1-5 patches (have been merged)
> - modify commit message
> - use readl_poll_timeout_atomic() in wait_pio_xfer()
> - use msecs_to_jiffies() when get PIO mode timeout value
> - factor out transfer state handling into spacemit_i2c_handle_state().
> - do not disable/enable the controller IRQ around PIO transfers.
> - consolidate spacemit_i2c_init() interrupt setup
> - rename is_pio -> use_pio
> - rename spacemit_i2c_xfer() -> spacemit_i2c_xfer_common()
> - rename spacemit_i2c_int_xfer() -> spacemit_i2c_xfer()
> - rename spacemit_i2c_pio_xfer() -> spacemit_i2c_pio_xfer_atomic()
> - call spacemit_i2c_err_check() in wait_pio_xfer() when write last byte
> - Link to v2: https://lore.kernel.org/r/20250925-k1-i2c-atomic-v2-0-46dc13311cda@linux.spacemit.com
> 
> Changes in v2:
> - Patch 1/6:
>   Patch 3/6:
>   Patch 4/6:
>     - nothing
> - Patch 2/6:
>   - remove is_pio judgement in irq_handler()
> - Patch 5/6:
>   - fix wrong comment
>   - In spacemit_i2c_conditionally_reset_bus(), once the condition is met inside the loop, it should
>     return directly instead of using break.
> - Patch 6/6:
>   - add is_pio judgement in irq_handler()
>   - use a fixed timeout value when PIO
>   - use readl_poll_timeout() in  spacemit_i2c_wait_bus_idle() when PIO
> 
> - Link to v1: https://lore.kernel.org/r/20250827-k1-i2c-atomic-v1-0-e59bea02d680@linux.spacemit.com
> ---
>  drivers/i2c/busses/i2c-k1.c | 206 ++++++++++++++++++++++++++++++++++----------
>  1 file changed, 161 insertions(+), 45 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-k1.c b/drivers/i2c/busses/i2c-k1.c
>  static int spacemit_i2c_xfer_msg(struct spacemit_i2c_dev *i2c)
>  {
>  	unsigned long time_left;
> @@ -310,10 +376,16 @@ static int spacemit_i2c_xfer_msg(struct spacemit_i2c_dev *i2c)
>  
>  		reinit_completion(&i2c->complete);
>  
> -		spacemit_i2c_start(i2c);
> +		if (i2c->use_pio) {
> +			spacemit_i2c_start(i2c);
> +
> +			time_left = spacemit_i2c_wait_pio_xfer(i2c);
> +		} else {
> +			spacemit_i2c_start(i2c);
I will put i2c_start() out in the next version.

                        - Troy