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From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Fabio Estevam <festevam@gmail.com>
Cc: Abel Vesa <abelvesa@kernel.org>,
	Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>, Shawn Guo <shawnguo@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	NXP Linux Team <linux-imx@nxp.com>,
	linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org
Subject: Re: [PATCH] clk: imx8mp: register driver at arch_initcall time
Date: Sat, 19 Nov 2022 22:57:02 +0100	[thread overview]
Message-ID: <09611b2d-096e-058b-5349-627684e3a13c@rasmusvillemoes.dk> (raw)
In-Reply-To: <CAOMZO5BPtEU6VCZXRk5FTHXDad6cegF=+oHTTA0wgjBuoh9-rQ@mail.gmail.com>

On 19/11/2022 22.38, Fabio Estevam wrote:
> On Wed, Sep 28, 2022 at 9:41 AM Rasmus Villemoes
> <linux@rasmusvillemoes.dk> wrote:
>>
>> We have an imx8mp-based board with an external gpio-triggered
>> watchdog. Currently, we don't get to handle that in time before it
>> resets the board.
>>
>> The probe of the watchdog device gets deferred because the SOC's GPIO
>> controller is not yet ready, and the probe of that in turn gets deferred
>> because its clock provider (namely, this driver) is not yet
>> ready. Altogether, the watchdog does not get handled until the late
>> initcall deferred_probe_initcall has made sure all leftover devices
>> have been probed, and that's way too late.
>>
>> Aside from being necessary for our board, this also reduces total boot
>> time because fewer device probes get deferred.
>>
>> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
>> ---
>> It would probably be reasonable to do the same to the other imx8m* clk
>> drivers, but I don't have any such hardware to test on.
> 
> Agreed.
> 
>> +static void __exit imx8mp_clk_exit(void)
>> +{
>> +       platform_driver_unregister(&imx8mp_clk_driver);
>> +}
>> +module_exit(imx8mp_clk_exit);
> 
> Isn't module_exit() unnecessary here, since we pass suppress_bind_attrs = true?

Sorry, I don't follow. Before this patch, the driver also implicitly had
a module_exit() doing exactly this platform_driver_unregister(), it was
just hidden inside the module_platform_driver() macro. And I think
that's necessary if one wants to test that the module can be loaded and
unloaded (I don't think it's ever useful or even possible to have it be
a module on an actual imx8mp board).

For a modular build, this patch changes nothing since all foo_initcall
levels are translated to module_initcall for those. And when the driver
is built-in, the __exit code, both before and after this patch, is
discarded in the final image.

Rasmus


  reply	other threads:[~2022-11-19 21:57 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-28 12:41 [PATCH] clk: imx8mp: register driver at arch_initcall time Rasmus Villemoes
2022-10-24 13:48 ` Rasmus Villemoes
2022-10-24 14:00   ` Ahmad Fatoum
2022-10-24 14:31     ` Rasmus Villemoes
2022-10-27 23:29 ` Stephen Boyd
2022-10-31  9:15   ` Rasmus Villemoes
2022-11-07 13:54 ` Rasmus Villemoes
2022-11-19 20:45   ` Rasmus Villemoes
2022-11-19 21:38 ` Fabio Estevam
2022-11-19 21:57   ` Rasmus Villemoes [this message]
2022-11-19 22:02     ` Fabio Estevam
2022-11-21  9:44       ` Rasmus Villemoes
2022-11-21 10:59         ` Fabio Estevam
2022-11-21 12:29           ` Rasmus Villemoes
2022-11-21 12:48             ` Fabio Estevam
2022-11-21 15:43 ` Abel Vesa
2022-11-22  7:49   ` Rasmus Villemoes
2022-11-23  1:42     ` Stephen Boyd

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