linux-kernel - Re: microcode loading got really slow.

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Message-ID: <CACVXFVNO9FeCaJ_YFbvPMUHOBjneLqqW+ucYprZb7884Eth-DA@mail.gmail.com>
Date:	Thu, 23 May 2013 18:45:29 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	Dave Jones <davej@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>, x86@...nel.org,
	fenghua.yu@...el.com
Subject: Re: microcode loading got really slow.

On Thu, May 23, 2013 at 6:36 PM, Takashi Iwai <tiwai@...e.de> wrote:
>
> No, f/w loader always fall back to user mode helper, as long as its
> support is built in.  And doing that for microcode driver in that code
> path isn't only superfluous but also broken due to request_firmware
> call in module init.

Firstly, it is not good to do this since some distributions doesn't support
direct loading and doesn't have udevd(such as, android).

Secondly, returning failure from request_firmware_direct() doesn't mean
the firmware doesn't exist since distribution may put the firmware other where.

Anyway, this example is very specific(no firmware can be accepted), and
request_firmware_nowait() should be OK for the situation.

>
>> wrt. this problem, I think we
>> need to know why the direct loading is failed.
>
> The reason is obvious: the requested f/w file doesn't exist.
> And it's fine, because the microcode update is an optional operation.
> If no f/w file is found, it's not handled as an error.  It just means
> that no need to update, continuing to work.

OK, as said above, the example is very specific, and might be
workarounded by request_firmware_nowait().


Thanks,
-- 
Ming Lei
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