linux-kernel - Re: [PATCH v4] i2c: imx: support DMA defer probing

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Message-ID: <20241127-attentive-orthodox-tuna-8f8af0-mkl@pengutronix.de>
Date: Wed, 27 Nov 2024 09:42:40 +0100
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: carlos.song@....com
Cc: frank.li@....com, 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 v4] i2c: imx: support DMA defer probing

On 27.11.2024 16:38:18, 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.
> 
> 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>
> ---
> Change for V4:
> - Output "Only use PIO mode" log in debug level when no DMA configure.
> Change for V3:
> - According to Marc's comment, remove error print when defer probe.
>   Add info log when DMA has not been enabled and add error log when
>   DMA error, both won't stuck the i2c adapter register, just for reminding,
>   i2c adapter is working only in PIO mode.
> 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 | 31 +++++++++++++++++++++++--------
>  1 file changed, 23 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 5ed4cb61e262..b11d66d56c55 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;

Why is this change needed? What's the purpose?

>  	int ret;
>  
>  	dma = devm_kzalloc(dev, sizeof(*dma), GFP_KERNEL);

This means you bind the allocated memory to the parent device, not the
i2c device anymore.

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
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