linux-kernel - Re: [PATCH v2] b43: Replace mdelay with usleep_range in b43_radio_2057_init

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Message-ID: <4201e8cd-81ba-ab7d-2a0d-af957c5dfed6@gmail.com>
Date:   Tue, 9 Jan 2018 16:39:31 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Larry.Finger@...inger.net, kvalo@...eaurora.org,
        kstewart@...uxfoundation.org, johannes.berg@...el.com,
        tiwai@...e.de, colin.king@...onical.com,
        andrew.zaborowski@...el.com, linux-kernel@...r.kernel.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        b43-dev@...ts.infradead.org
Subject: Re: [PATCH v2] b43: Replace mdelay with usleep_range in
 b43_radio_2057_init_post



On 2018/1/9 16:35, Greg KH wrote:
> On Tue, Jan 09, 2018 at 09:40:06AM +0800, 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 usleep_range,
>> to reduce busy wait.
>>
>> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
>> ---
>> v2:
>> * Replace mdelay with usleep_range, instead of msleep in v1.
>>    Thank Larry for good advice.
>> ---
>>   drivers/net/wireless/broadcom/b43/phy_n.c |    2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/wireless/broadcom/b43/phy_n.c b/drivers/net/wireless/broadcom/b43/phy_n.c
>> index a5557d7..f2a2f41 100644
>> --- a/drivers/net/wireless/broadcom/b43/phy_n.c
>> +++ b/drivers/net/wireless/broadcom/b43/phy_n.c
>> @@ -1031,7 +1031,7 @@ static void b43_radio_2057_init_post(struct b43_wldev *dev)
>>   
>>   	b43_radio_set(dev, R2057_RFPLL_MISC_CAL_RESETN, 0x78);
>>   	b43_radio_set(dev, R2057_XTAL_CONFIG2, 0x80);
>> -	mdelay(2);
>> +	usleep_range(2000, 3000);
> Where did 3000 come from?  Are you sure about that?

I am not very sure, and I use it according to Larry's message:

> I had negative comments on one of those due to the possibility of
> msleep(2) extending as long as 20 msec. Until the author, or someone
> else, can test that this is OK, then the mdelay(2) can only be
> replaced with usleep_range(2000, 3000).

Thanks,
Jia-Ju Bai