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List:       linux-wireless
Subject:    Re: [PATCH] wifi: rtlwifi: rtl_usb: Use sync register writes
From:       Bitterblue Smith <rtl8821cerfe2 () gmail ! com>
Date:       2023-12-30 13:12:20
Message-ID: 1408a85d-48c4-4427-a5e0-a81c3cf10385 () gmail ! com
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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.


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