linux-kernel - Re: [PATCH v2 2/2] mwifiex: pcie: add reset_d3cold quirk for Surface gen4+ devices

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Message-ID: <89c9d1b8-c204-d028-9f2c-80d580dabb8b@gmail.com>
Date:   Sat, 10 Jul 2021 02:00:08 +0200
From:   Maximilian Luz <luzmaximilian@...il.com>
To:     Pali Rohár <pali@...nel.org>
Cc:     Jonas Dreßler <verdre@...d.nl>,
        Amitkumar Karwar <amitkarwar@...il.com>,
        Xinming Hu <huxinming820@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Tsuchiya Yuto <kitakar@...il.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v2 2/2] mwifiex: pcie: add reset_d3cold quirk for Surface
 gen4+ devices

On 7/10/21 12:54 AM, Pali Rohár wrote:

[...]

>> Also not sure if this is just my bias, but it feels like the Surface
>> line always had more problems with that driver (and firmware) than
>> others.
> 
> Ehm, really? I see reports also from non-Surface users about bad quality
> of these 88W[89]xxx cards and repeating firmware issues. I have bad
> personal experience with 88W8997 SDIO firmware and lot of times I get
> advice about ex-Marvell/NXP wifi cards "do not touch and run away
> quickly".

Yeah, then I'm probably biased since I'm mostly dealing with Surface
stuff.

> I think that more people if they get mPCIe/M.2 wifi card in laptop which
> does not work, they just replace it with some working one. And not
> spending infinite time in trying to fix it... So this may explain why
> there are more Surface users with these issues...

That might be an explanation. If it wouldn't need a heat-gun to open it
up, I'd probably have done that at some point in the past (there were
times when WiFi at my Uni was pretty much unusable with this device...
and I'm still not sure what fixed that or even if it's fixed completely).

>> I'm honestly a bit surprised that MS stuck with them for this
>> long (they decided to go with Intel for 7th gen devices). AFAICT they
>> initially chose Marvell due to connected standby support, so maybe that
>> causes issue for us and others simply aren't using that feature? Just
>> guessing though.
> 
> In my opinion that "Connected Standby" is just MS marketing term.

I can only really repeat what I've been told: Apparently when they
started designing those devices, the only option with "Connected
standby" (or probably rather that feature set that MS wanted) was,
unfortunately for us, Marvell.

> 88W[89]xxx chips using full-mac firmware and drivers [*]. Full-mac lot
> of times causing more issues than soft-mac solution. Moreover this
> Marvell firmware implements also other "application" layers in firmware
> which OS drivers can use, e.g. there is fully working "wpa-supplicant"
> replacement and also AP part. Maybe windows drivers are using it and it
> cause less problems? Duno. mwifiex uses only "low level" commands and
> WPA state machine is implemented in userspace wpa-supplicant daemon.
> 
> [*] - Small note: There are also soft-mac firmwares and drivers but
> apparently Marvell has never finished linux driver and firmware was not
> released to public...
> 
> And there is also Laird Connectivity which offers their own proprietary
> linux kernel drivers with their own firmware for these 88W[89]xxx chips.
> Last time I checked it they released some parts of driver on github.
> Maybe somebody could contact Laird or check if their driver can be
> replaced by mwifiex? Or just replacing ex-Marvell/NXP firmware by their?
> But I'm not sure if they have something for 88W8897.

Interesting, I was not aware of this. IIRC we've been experimenting with
the mwlwifi driver (which that lrdmwl driver seems to be based on?), but
couldn't get that to work with the firmware we have. IIRC it also didn't
work with the Windows firmware (which seems to be significantly
different from the one we have for Linux and seems to use or be modeled
after some special Windows WiFi driver interface).