linux-kernel - Re: [PATCH v4] i2c: spacemit: introduce pio for k1

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Message-ID: <aQvP4HVcpX-MDZBJ@aurel32.net>
Date: Wed, 5 Nov 2025 23:29:52 +0100
From: Aurelien Jarno <aurelien@...el32.net>
To: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
Cc: 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 v4] i2c: spacemit: introduce pio for k1

Hi,

On 2025-10-09 17:59, 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 v4:
> - refactor for better readability: simplify condition check and moving if/else (timeout/
>   wait_xfer_complete) logic into a function
> - remove irrelevant changes
> - remove the status clear call in spacemit_i2c_xfer_common()
> - sort functions to avoid forward declarations,
>   move unavoidable ones above function definitions
> - use udelay() in atomic context to avoid sleeping
> - wait for MSD on the last byte in wait_pio_xfer()
> - Link to v3: https://lore.kernel.org/r/20250929-k1-i2c-atomic-v3-1-f7e660c138b6@linux.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 | 229 +++++++++++++++++++++++++++++++++++---------
>  1 file changed, 185 insertions(+), 44 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-k1.c b/drivers/i2c/busses/i2c-k1.c
> index 6b918770e612e098b8ad17418f420d87c94df166..a13284f840ee967466a01375e6603f7568a42f86 100644
> --- a/drivers/i2c/busses/i2c-k1.c
> +++ b/drivers/i2c/busses/i2c-k1.c
> @@ -97,6 +97,8 @@
>  
>  #define SPACEMIT_BUS_RESET_CLK_CNT_MAX		9
>  
> +#define SPACEMIT_WAIT_TIMEOUT      1000 /* ms */
> +
>  enum spacemit_i2c_state {
>  	SPACEMIT_STATE_IDLE,
>  	SPACEMIT_STATE_START,
> @@ -125,10 +127,14 @@ struct spacemit_i2c_dev {
>  
>  	enum spacemit_i2c_state state;
>  	bool read;
> +	bool use_pio;
>  	struct completion complete;
>  	u32 status;
>  };
>  
> +static void spacemit_i2c_err_check(struct spacemit_i2c_dev *i2c);
> +static void spacemit_i2c_handle_state(struct spacemit_i2c_dev *i2c);
> +

At least for spacemit_i2c_err_check, the forward declaration can be 
avoided by moving code, which is anyway probably better done in a 
separate patch.

Besides this nitpick, this sounds good, so:

Tested-by: Aurelien Jarno <aurelien@...el32.net>
Reviewed-by: Aurelien Jarno <aurelien@...el32.net>

Regards
Aurelien

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@...el32.net                     http://aurel32.net