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

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Message-ID: <f2690b83-b907-4ade-bb9d-daa0636c6786@pengutronix.de>
Date: Fri, 20 Dec 2024 11:51:27 +0100
From: Ahmad Fatoum <a.fatoum@...gutronix.de>
To: Carlos Song <carlos.song@....com>,
 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>
Subject: Re: [PATCH v5] i2c: imx: support DMA defer probing

Hi Carlos,

On 20.12.24 11:46, Carlos Song wrote:
> 
> 
>> -----Original Message-----
>> From: Ahmad Fatoum <a.fatoum@...gutronix.de>
>> Sent: Friday, December 20, 2024 5:32 PM
>> To: Carlos Song <carlos.song@....com>; Oleksij Rempel

>> I know -110, but -12 I need to look up :) Both are cryptic to end users, which is
>> why %pe was added on top of the existing %p:
>>
>> If CONFIG_SYMBOLIC_ERRNAME is enabled %pe expands to an error string, e.g.
>> "ENOMEM" or "ETIMEDOUT". If it's disabled, you get the same error number
>> that was printed raw before.
>>
>> Cheers,
>> Ahmad
>>
> 
> Wow! Looks so cool.
> Thank you very much for your patient explanation! I agree it.
> 
> Also I will change the comment from your suggestion[1]:
> 
> "
>   /*
>    * As we can always fall back to PIO, let's ignore the error setting up
>    * DMA and see if we run into errors while setting up PIO mode.
>    */
> "
> In fact, other errors are also from DMA setting not from setting PIO mode.
> So can I comment simply like this?
> 
>         /* As we can always fall back to PIO, let's ignore the error setting up DMA. */
>         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 (%pe), only use PIO mode\n", ERR_PTR(ret));
>         }
> 
> [1]https://lore.kernel.org/imx/89a3b1c9-2be2-4e7f-a0c6-abbf8b88957b@pengutronix.de/

Sure, looks good to me. @Oleksij?

Cheers,
Ahmad

> 
> BR
> Carlos
>>>
>>> i2c_imx_dma_request is using PTR_ERR to convert pointer to error value[1].
>>> I don't know why need to use ERR_PTR to reconvert the value to pointer:
>>>
>>> dev_err(&pdev->dev, "Failed to setup DMA (%pe), only use PIO mode\n",
>>> ERR_PTR(ret));
>>>
>>> Is there some strong reason?
>>>
>>> [1]
>>> https://lore/
>>> .kernel.org%2Fimx%2FAM0PR0402MB3937419BBB58B75FB8F8DE2DE8072%
>> 40AM0PR04
>>>
>> 02MB3937.eurprd04.prod.outlook.com%2F&data=05%7C02%7Ccarlos.song%4
>> 0nxp
>>> .com%7C13a8e6532dd7435c302008dd20d92819%7C686ea1d3bc2b4c6fa92c
>> d99c5c30
>>>
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>> FbXB0eU1h
>>>
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>>>
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>> cGhFL2G%2F
>>> ECNek%3D&reserved=0
>>>>
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>>>> Pengutronix e.K.                           |
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>>>> Steuerwalder Str. 21                       |
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>> 2008d
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>> 922763
>>>>
>> 8077%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjA
>> uMDAw
>>>>
>> MCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&s
>> da
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>> 0
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>>>> %7C638702808104903131%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hc
>> Gki
>>>>
>> OnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyf
>>>>
>> Q %3D%3D%7C0%7C%7C%7C&sdata=EnhsIFlBooqjB%2FSRWF7uAqRHE3yN6rbd
>> D
>>>> 1yQueTrRus%3D&reserved=0  |
>>>> 31137 Hildesheim, Germany                  | Phone:
>> +49-5121-206917-0
>>>> |
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>>
>> --
>> Pengutronix e.K.                           |
>> |
>> Steuerwalder Str. 21                       |
>> http://www.pen/
>> gutronix.de%2F&data=05%7C02%7Ccarlos.song%40nxp.com%7C13a8e6532dd
>> 7435c302008dd20d92819%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0
>> %7C638702839227652725%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGki
>> OnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ
>> %3D%3D%7C0%7C%7C%7C&sdata=Hm60QL5dJ2h3OCesOXK871ASnK7s0L4SPiY
>> bK0jtSOo%3D&reserved=0  |
>> 31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0
>> |
>> Amtsgericht Hildesheim, HRA 2686           | Fax:
>> +49-5121-206917-5555 |


-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |