linux-kernel - Re: [PATCH] b43: Replace mdelay with msleep in b43_radio_2057_init

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Message-ID: <906de5ba-b572-ada0-68ad-5e161ef6016e@lwfinger.net>
Date:   Sat, 30 Dec 2017 12:49:50 -0600
From:   Larry Finger <Larry.Finger@...inger.net>
To:     Jia-Ju Bai <baijiaju1990@...il.com>, kvalo@...eaurora.org,
        colin.king@...onical.com, johannes.berg@...el.com, tiwai@...e.de,
        kstewart@...uxfoundation.org, gregkh@...uxfoundation.org,
        andrew.zaborowski@...el.com
Cc:     linux-wireless@...r.kernel.org, b43-dev@...ts.infradead.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] b43: Replace mdelay with msleep in
 b43_radio_2057_init_post

On 12/30/2017 05:08 AM, Jia-Ju Bai wrote:
> b43_radio_2057_init_post is not called in an interrupt handler
> nor holding a spinlock.
> The function mdelay in it can be replaced with msleep, to reduce busy wait.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>

checkpatch.pl reports the following warning for this patch:

WARNING: msleep < 20ms can sleep for up to 20ms; see 
Documentation/timers/timers-howto.txt
#26: FILE: drivers/net/wireless/broadcom/b43/phy_n.c:1034:
+       msleep(2);

total: 0 errors, 1 warnings, 0 checks, 8 lines checked

Have you tested to verify that a sleep as long as 20 ms will not cause problems? 
The referenced document suggests a usleep_range() call.

In general, delay changes should never be proposed without testing.

Larry