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

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Message-ID: <555069e4-dd2c-b17a-d44f-9258558cb98d@gmail.com>
Date:   Tue, 9 Jan 2018 17:47:58 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     Arend van Spriel <arend.vanspriel@...adcom.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 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.


Thanks,
Jia-Ju Bai