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Sender: Larry Finger <larry.finger@gmail.com>
Message-ID: <287e9d4e-316a-4579-961e-58e75abea534@lwfinger.net>
Date: Wed, 10 Apr 2024 21:47:58 -0500
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Subject: Re: [RFC] rtw88: Fix startup problems for SDIO wifi plus UART
 Bluetooth
To: Ping-Ke Shih <pkshih@realtek.com>, Larry Finger <Larry.Finger@gmail.com>,
 Kalle Valo <kvalo@kernel.org>
Cc: Johannes Berg <johannes@sipsolutions.net>,
 "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
 "stable@vger.kernel.org" <stable@vger.kernel.org>
References: <4umro86wvv84.MjDfYvt4P5uZryt8boBK8Q2@1EHFQ.trk.elasticemail.com>
 <5af71338f3904aac9d2c237637c851e7@realtek.com>
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From: Larry Finger <Larry.Finger@lwfinger.net>
In-Reply-To: <5af71338f3904aac9d2c237637c851e7@realtek.com>
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On 4/10/24 9:13 PM, Ping-Ke Shih wrote:
> 
> Larry Finger <Larry.Finger@gmail.com> wrote:
> 
>> As discussed in the links below, the SDIO part of RTW8821CS fails to
>> start correctly if such startup happens while the UART portion of
>> the chip is initializing.
> 
> I checked with SDIO team internally, but they didn't meet this case, so we may
> take this workaround.
> 
> SDIO team wonder if something other than BT cause this failure, and after
> system boots everything will be well. Could you boot the system without WiFi/BT
> drivers, but insmod drivers manually after booting?

I sent the request to the user with the problem. I do not have any SDIO devices.

> 
> 
>> ---
>>   drivers/net/wireless/realtek/rtw88/sdio.c | 28 +++++++++++++++++++++++
>>   1 file changed, 28 insertions(+)
>>
>> diff --git a/drivers/net/wireless/realtek/rtw88/sdio.c b/drivers/net/wireless/realtek/rtw88/sdio.c
>> index 0cae5746f540..eec0ad85be72 100644
>> --- a/drivers/net/wireless/realtek/rtw88/sdio.c
>> +++ b/drivers/net/wireless/realtek/rtw88/sdio.c
>> @@ -1325,6 +1325,34 @@ int rtw_sdio_probe(struct sdio_func *sdio_func,
> 
> [...]
> 
>> +       mdelay(500);
> 
> Will it better to use sleep function?

My thoughts were that a sleep function would tie up a CPU, whereas the delay 
would not. Initially, we tested an msleep(150) statement, but that only gave a 
60% success rate, whereas mdelay(500) worked 20 straight tries.

Thanks for your comments.

Larry