linux-kernel - Re: [PATCH] i2c: imx: support DMA defer probing

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Message-ID: <Z0SxCcnPOPA60i26@lizhi-Precision-Tower-5810>
Date: Mon, 25 Nov 2024 12:16:57 -0500
From: Frank Li <Frank.li@....com>
To: carlos.song@....com
Cc: o.rempel@...gutronix.de, kernel@...gutronix.de, andi.shyti@...nel.org,
	shawnguo@...nel.org, s.hauer@...gutronix.de, festevam@...il.com,
	linux-i2c@...r.kernel.org, imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: imx: support DMA defer probing

On Mon, Nov 25, 2024 at 09:52:43PM +0800, carlos.song@....com wrote:
> From: Carlos Song <carlos.song@....com>
>
> Return -EPROBE_DEFER when dma_request_slave_channel() because
> DMA driver have not ready yet.

wrap at 75 char.

>
> Move i2c_imx_dma_request() before registering I2C adapter to avoid
> infinite loop of .probe() calls to the same driver, see "e8c220fac415
> Revert "i2c: imx: improve the error handling in i2c_imx_dma_request()""
> and "Documentation/driver-api/driver-model/driver.rst".
>
> Use CPU mode to avoid stuck registering i2c adapter when DMA resources
> are unavailable.
>
> Signed-off-by: Carlos Song <carlos.song@....com>
> Signed-off-by: Clark Wang <xiaoning.wang@....com>
> ---
>  drivers/i2c/busses/i2c-imx.c | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 5ed4cb61e262..ee7070ee9e6e 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -397,17 +397,16 @@ static void i2c_imx_reset_regs(struct imx_i2c_struct *i2c_imx)
>  }
>
>  /* Functions for DMA support */
> -static void i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
> -						dma_addr_t phy_addr)
> +static int i2c_imx_dma_request(struct device *dev, dma_addr_t phy_addr)
>  {

Not sure why you change "struct imx_i2c_struct *i2c_imx" to
"struct device *dev"

> +	struct imx_i2c_struct *i2c_imx = dev_get_drvdata(dev);
>  	struct imx_i2c_dma *dma;
>  	struct dma_slave_config dma_sconfig;
> -	struct device *dev = &i2c_imx->adapter.dev;
>  	int ret;
>
>  	dma = devm_kzalloc(dev, sizeof(*dma), GFP_KERNEL);
>  	if (!dma)
> -		return;
> +		return -ENOMEM;
>
>  	dma->chan_tx = dma_request_chan(dev, "tx");
>  	if (IS_ERR(dma->chan_tx)) {
> @@ -452,7 +451,7 @@ static void i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
>  	dev_info(dev, "using %s (tx) and %s (rx) for DMA transfers\n",
>  		dma_chan_name(dma->chan_tx), dma_chan_name(dma->chan_rx));
>
> -	return;
> +	return 0;
>
>  fail_rx:
>  	dma_release_channel(dma->chan_rx);
> @@ -460,6 +459,8 @@ static void i2c_imx_dma_request(struct imx_i2c_struct *i2c_imx,
>  	dma_release_channel(dma->chan_tx);
>  fail_al:
>  	devm_kfree(dev, dma);
> +
> +	return ret;
>  }
>
>  static void i2c_imx_dma_callback(void *arg)
> @@ -1803,6 +1804,13 @@ static int i2c_imx_probe(struct platform_device *pdev)
>  	if (ret == -EPROBE_DEFER)
>  		goto clk_notifier_unregister;
>
> +	/* Init DMA config if supported */
> +	ret = i2c_imx_dma_request(&pdev->dev, phy_addr);
> +	if (ret == -EPROBE_DEFER) {
> +		dev_err(&pdev->dev, "DMA not ready, go defer probe!\n");
> +		goto clk_notifier_unregister;
> +	}
> +
>  	/* Add I2C adapter */
>  	ret = i2c_add_numbered_adapter(&i2c_imx->adapter);
>  	if (ret < 0)
> @@ -1817,9 +1825,6 @@ static int i2c_imx_probe(struct platform_device *pdev)
>  		i2c_imx->adapter.name);
>  	dev_info(&i2c_imx->adapter.dev, "IMX I2C adapter registered\n");
>
> -	/* Init DMA config if supported */
> -	i2c_imx_dma_request(i2c_imx, phy_addr);
> -
>  	return 0;   /* Return OK */
>
>  clk_notifier_unregister:
> --
> 2.34.1
>