linux-kernel - Re: [PATCH v3] i2c: imx-lpi2c: change to PIO mode in system-wide suspend/resume progress

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Message-ID: <aR/afqVB3icwsDV/@lizhi-Precision-Tower-5810>
Date: Thu, 20 Nov 2025 22:20:30 -0500
From: Frank Li <Frank.li@....com>
To: Carlos Song <carlos.song@....com>
Cc: aisheng.dong@....com, andi.shyti@...nel.org, shawnguo@...nel.org,
	s.hauer@...gutronix.de, kernel@...gutronix.de,
	linux-i2c@...r.kernel.org, imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] i2c: imx-lpi2c: change to PIO mode in system-wide
 suspend/resume progress

On Fri, Nov 21, 2025 at 11:00:30AM +0800, Carlos Song wrote:
> EDMA resumes early and suspends late in the system power transition
> sequence, while LPI2C enters the NOIRQ stage for both suspend and resume.
> This means LPI2C resources become available before EDMA is fully resumed.
> Once IRQs are enabled, a slave device may immediately trigger an LPI2C
> transfer. If the transfer length meets DMA requirements, the driver will
> attempt to use EDMA even though EDMA may still be unavailable.
>
> This timing gap can lead to transfer failures. To prevent this, force
> LPI2C to use PIO mode during system-wide suspend and resume transitions.
> This reduces dependency on EDMA and avoids using an unready DMA resource.
>
> Fixes: a09c8b3f9047 ("i2c: imx-lpi2c: add eDMA mode support for LPI2C")
> Signed-off-by: Carlos Song <carlos.song@....com>
>
> ---

Reviewed-by: Frank Li <Frank.Li@....com>

> Changes since v2:
> * Updated commit message as per discussion with Frank and improve the
>   commit log by AI
> Changes since v1:
> * Updated commit message as per discussion with Frank.
> ---
>  drivers/i2c/busses/i2c-imx-lpi2c.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
> index 2a0962a0b441..d882126c1778 100644
> --- a/drivers/i2c/busses/i2c-imx-lpi2c.c
> +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
> @@ -592,6 +592,13 @@ static bool is_use_dma(struct lpi2c_imx_struct *lpi2c_imx, struct i2c_msg *msg)
>  	if (!lpi2c_imx->can_use_dma)
>  		return false;
>
> +	/*
> +	 * A system-wide suspend or resume transition is in progress. LPI2C should use PIO to
> +	 * transfer data to avoid issue caused by no ready DMA HW resource.
> +	 */
> +	if (pm_suspend_in_progress())
> +		return false;
> +
>  	/*
>  	 * When the length of data is less than I2C_DMA_THRESHOLD,
>  	 * cpu mode is used directly to avoid low performance.
> --
> 2.34.1
>