[PATCH v2] i2c: imx: support DMA defer probing

[Marc Kleine-Budde]

On 26.11.2024 16:25:35, carlos.song at nxp.com wrote:
> From: Carlos Song <carlos.song at nxp.com>
> 
> Return -EPROBE_DEFER when dma_request_slave_channel() because DMA driver
> have not ready yet.
> 
> 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 at nxp.com>
> Signed-off-by: Clark Wang <xiaoning.wang at nxp.com>
> ---
> Change for V2:
> - According to Frank's comments, wrap at 75 char and Simplify fix code
>   at i2c_imx_dma_request().
> - Use strict patch check, fix alignment warning at i2c_imx_dma_request()
> ---
>  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..4e5633166a1e 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 imx_i2c_struct *i2c_imx, dma_addr_t phy_addr)
>  {
>  	struct imx_i2c_dma *dma;
>  	struct dma_slave_config dma_sconfig;
> -	struct device *dev = &i2c_imx->adapter.dev;
> +	struct device *dev = i2c_imx->adapter.dev.parent;
>  	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(i2c_imx, phy_addr);
> +	if (ret == -EPROBE_DEFER) {
> +		dev_err(&pdev->dev, "DMA not ready, go defer probe!\n");
> +		goto clk_notifier_unregister;
> +	}

Don't spam the logs if the driver defers probing, it's not a error. And
it looks strange to ignore all other errors here. Either add a comment
here, something like "continue without DMA", or let the function return
0 in case the driver should continue and propagate the error if the
caller should take care of it.

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung Nürnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |
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