linux-kernel - Re: [PATCH v2] i2c: imx: support DMA defer probing

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Message-ID: <20241126-paper-nightingale-of-wealth-de17e7-mkl@pengutronix.de>
Date: Tue, 26 Nov 2024 11:23:53 +0100
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Carlos Song <carlos.song@....com>
Cc: Frank Li <frank.li@....com>, 
	"o.rempel@...gutronix.de" <o.rempel@...gutronix.de>, "kernel@...gutronix.de" <kernel@...gutronix.de>, 
	"andi.shyti@...nel.org" <andi.shyti@...nel.org>, "shawnguo@...nel.org" <shawnguo@...nel.org>, 
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>, "festevam@...il.com" <festevam@...il.com>, 
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>, "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>, 
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] i2c: imx: support DMA defer probing

On 26.11.2024 10:15:27, Carlos Song wrote:
> > >  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.
> > 
> 
> Hi,
> Thank you for your suggestion! I agree with you.
> I will change to this logic:
> 	ret = i2c_imx_dma_request(i2c_imx, phy_addr);
> 	if (ret) {
> 		if (ret == -EPROBE_DEFER)
> 			goto clk_notifier_unregister;
> 		dev_info(&pdev->dev, "use pio mode\n");
> 	}
> 
> Ret = 0  ----->  enable DMA successfully  -------> no print
> Ret!=0  ----->  defer probe ---------> no print and try again
> Ret!=0  ----->  fail to enable DMA ------> remind now is using pio mode
> 
> Do you think the logic is acceptable?

Yes, the other option is to move the logic into i2c_imx_dma_request()
and let it return 0 in case of DMA or fallback to PIO, or an error in
case of probe defer or a fatal error.

This way the probe function will look like this:

     ret = i2c_imx_dma_request(i2c_imx, phy_addr);
     if (ret)
                return dev_err_probe(&pdev->dev, ret, "Failed to setup DMA\n");


regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
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