linux-kernel - Re: [PATCH v4 2/2] Bluetooth: hci_h5: Add power reset via gpio in h5_btrtl

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Message-ID: <57978333-f2d2-ca7e-947b-8d184fe30d94@lexina.in>
Date:   Thu, 20 Jan 2022 09:13:03 +0300
From:   Vyacheslav <adeep@...ina.in>
To:     Marcel Holtmann <marcel@...tmann.org>
Cc:     Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] Bluetooth: hci_h5: Add power reset via gpio in
 h5_btrtl_open

Hi!

19.01.2022 22:32, Marcel Holtmann wrote:
> Hi Vyacheslav,
> 
>> Add power reset via enable-gpios in h5_btrtl_open function.
> 
> this is too sparse commit message. Add explation and if possible also references on why that is needed.

While testing the RTL8822CS SDIO WiFi/BT adapter, I found that in some 
cases the kernel could not initialize it. However, manually resetting 
the adapter via gpio allows it to start correctly.
Apparently at system start the adapter is in an undefined state 
(including the unknown state of gpio after starting uboot). A forced 
reset helps to initialize the adapter in most cases. Experimentally it 
was found that 100ms is enough to reset.

Since I am new to wireless drivers feel free correct me.

-- 
Vyacheslav Bocharov