linux-kernel - Re: [PATCH v5] i2c: imx: support DMA defer probing

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Message-ID:
 <AM0PR0402MB393781D3109B1B3FF3C2529FE8072@AM0PR0402MB3937.eurprd04.prod.outlook.com>
Date: Fri, 20 Dec 2024 06:58:16 +0000
From: Carlos Song <carlos.song@....com>
To: Oleksij Rempel <o.rempel@...gutronix.de>
CC: Andi Shyti <andi.shyti@...nel.org>, Frank Li <frank.li@....com>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>, "shawnguo@...nel.org"
	<shawnguo@...nel.org>, "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"festevam@...il.com" <festevam@...il.com>, "linux-i2c@...r.kernel.org"
	<linux-i2c@...r.kernel.org>, "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Clark Wang <xiaoning.wang@....com>, Ahmad
 Fatoum <a.fatoum@...gutronix.de>
Subject: Re: [PATCH v5] i2c: imx: support DMA defer probing



> -----Original Message-----
> From: Oleksij Rempel <o.rempel@...gutronix.de>
> Sent: Friday, December 20, 2024 2:13 PM
> To: Carlos Song <carlos.song@....com>
> Cc: Andi Shyti <andi.shyti@...nel.org>; Frank Li <frank.li@....com>;
> kernel@...gutronix.de; 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; Clark Wang
> <xiaoning.wang@....com>; Ahmad Fatoum <a.fatoum@...gutronix.de>
> Subject: [EXT] Re: [PATCH v5] i2c: imx: support DMA defer probing
>
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>
> On Fri, Dec 20, 2024 at 05:59:38AM +0000, Carlos Song wrote:
> > > > So we make this logic. Anyway we let the I2C controller registered
> > > > whether
> > > DMA is available or not(except defer probe).
> > > > Ignoring ENODEV and EPROBE_DEFER makes it looks like nothing
> > > > happened if
> > > DMA is defer probed or not enabled(This is an expected).
> > > > However we still need i2c DMA status is known when meet an
> > > > unexpected
> > > error, so we use dev_err_probe() to print error.
> > >
> > > Why dev_err_probe() instead of dev_err()?
> > >
> > Hi,
> > In patch V2 discussion, Marc suggested just return dev_err_probe(),
> > but I don't accept it so I choose to use dev_err_probe() to print error in V3.[1]
> In this case, the two APIs have the same function, do you mean dev_err() is more
> suitable?
>
> Yes, dev_err_probe() should be used in combination with return. For
> example:
>   return dev_err_probe(...);
>
> It will pass the return value on exit of the function and optionally print of the
> error message if it is not EPROBE_DEFER. Practically it replace commonly used
> coding pattern:
>   if (ret == -EPROBE_DEFER) {
>     return ret;
>   } else if (ret) {
>     dev_err(..);
>     return ret;
>   }
>
Hi,

Get your good point. I will change my code in V6:
+       ret = i2c_imx_dma_request(i2c_imx, phy_addr);
+       if (ret) {
+               if (ret == -EPROBE_DEFER)
+                       goto clk_notifier_unregister;
+               else if (ret == -ENODEV)
+                       dev_dbg(&pdev->dev, "Only use PIO mode\n");
+               else
+                       dev_err(&pdev->dev, "Failed to setup DMA, only use PIO mode\n");
+       }

I think this is what you want to see, right?

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