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Message-ID: <1408a85d-48c4-4427-a5e0-a81c3cf10385@gmail.com>
Date: Sat, 30 Dec 2023 15:12:20 +0200
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Subject: Re: [PATCH] wifi: rtlwifi: rtl_usb: Use sync register writes
To: Larry Finger <Larry.Finger@lwfinger.net>,
 "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Cc: Ping-Ke Shih <pkshih@realtek.com>
References: <f806007e-8fba-4f29-8a38-f81d04bd4fb8@gmail.com>
 <ddaf8f07-5a7b-49a4-8ec1-2a28eee2279e@lwfinger.net>
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From: Bitterblue Smith <rtl8821cerfe2@gmail.com>
In-Reply-To: <ddaf8f07-5a7b-49a4-8ec1-2a28eee2279e@lwfinger.net>
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On 29/12/2023 23:36, Larry Finger wrote:
> On 12/29/23 14:51, Bitterblue Smith wrote:
>> Currently rtl_usb performs register writes using the async
>> usb_submit_urb() function. This appears to work fine for the RTL8192CU,
>> but the RTL8192DU (soon to be supported by rtlwifi) has a problem:
>> it transmits everything at the 1M rate in the 2.4 GHz band. (The 5 GHZ
>> band is still untested.)
>>
>> With this patch, rtl_usb performs the register writes using the
>> synchronous usb_control_msg() function, and the RTL8192DU works
>> normally. The RTL8192CU still works.
>>
>> The vendor drivers use the async writes in only one function,
>> rtl8192du_trigger_gpio_0 / rtl8192cu_trigger_gpio_0, which probably
>> doesn't even run in real life. They use sync writes everywhere else.
>>
>> Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
>> ---
>>
>> Larry, do you remember why, back in 2011, you chose to implement the
>> async writes?
> 
> Bitterblue,
> 
> That was code provided by Realtek from their USB group. I think they were in China, not Taiwan. At least the PCI and USB groups were in different countries. They provided the code, and I just cleaned it up. tested it, and submitted it. If the sync function works for the cu and du chips, go for it.
> 
> Larry
> 

Ahh, okay. I guess we'll never know why they did that.