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

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Date:   Tue, 9 Jan 2018 12:11:58 +0100
From:   Arend van Spriel <arend.vanspriel@...adcom.com>
To:     Jia-Ju Bai <baijiaju1990@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>, Larry.Finger@...inger.net
Cc:     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 1/9/2018 10:47 AM, Jia-Ju Bai wrote:
>
>
> On 2018/1/9 17:07, Arend van Spriel wrote:
>> On 1/9/2018 9:39 AM, Jia-Ju Bai wrote:
>>>
>>>
>>> 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:
>>
>> Hi Jia-Ju Bai,
>>
>> The duration here is for settling the registers so hardware can pick
>> it up. Right after this they are written again. Now this is during
>> initialization of the radio so not time critical, but probably
>> anything in the range of 2000..3000 would also have been fine.
>
> Hi Arend,
>
> Thanks for your detailed explanation :)
> So I think usleep_range(2000, 3000) is okay.

Sure.

Regards,
Arend