Re: [PATCH v3 3/3] ARM: at91: remove unnecessary of_platform_default_populate calls

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: "Rob Herring (Arm)" <robh@kernel.org>
Cc: Richard Weinberger <richard@nod.at>,
	 Vignesh Raghavendra <vigneshr@ti.com>,
	 Nicolas Ferre <nicolas.ferre@microchip.com>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	 Claudiu Beznea <claudiu.beznea@tuxon.dev>,
	 Russell King <linux@armlinux.org.uk>,
	linux-mtd@lists.infradead.org,
	 linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 3/3] ARM: at91: remove unnecessary of_platform_default_populate calls
Date: Wed, 29 Apr 2026 11:42:19 +0200	[thread overview]
Message-ID: <87lde6cdc4.fsf@bootlin.com> (raw)
In-Reply-To: <20260429-lushly-greasily-c14c01c1aee8@thorsis.com> (Alexander Dahl's message of "Wed, 29 Apr 2026 10:02:28 +0200")

Hi Alexander,

>     [    0.958298] bus: 'platform': add driver atmel-ebi
>     [    0.958451] platform 10000000.ebi: bus: 'platform': __driver_probe_device: matched device with driver atmel-ebi
>     [    0.958566] platform 10000000.ebi: error -EPROBE_DEFER: wait for supplier /ahb/apb/pinctrl@fffff400/ebi/ebi-data-lsb
>     [    0.958649] platform 10000000.ebi: Added to deferred list
>     [    0.959429] bus: 'platform': remove driver atmel-ebi
>     [    0.959540] driver: 'atmel-ebi': driver_release

Interesting.

If you look at the very last line of the driver, the EBI driver does not
use a standard "module_platform_driver" macro, it uses some kind of
run-once probe that is kept in an __init section:
https://elixir.bootlin.com/linux/v7.0.1/source/drivers/memory/atmel-ebi.c#L637

And this seems to be incompatible with probe deferrals:
https://elixir.bootlin.com/linux/v7.0.1/source/drivers/base/platform.c#L948

I would suggest trying something alone these lines:

--- a/drivers/memory/atmel-ebi.c
+++ b/drivers/memory/atmel-ebi.c
@@ -633,5 +633,6 @@ static struct platform_driver atmel_ebi_driver = {
                .of_match_table = atmel_ebi_id_table,
                .pm = &atmel_ebi_pm_ops,
        },
+       .probe = atmel_ebi_probe,
 };
-builtin_platform_driver_probe(atmel_ebi_driver, atmel_ebi_probe);
+builtin_platform_driver(atmel_ebi_driver);

Memory taken by the probe function will remain mapped. That seems to be
the drawback.

Thanks,
Miquèl

