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

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Message-ID: <bfbb3b4d-07f7-1b97-54f0-21eba4766798@gmail.com>
Date:   Sat, 10 Jul 2021 00:25:36 +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 7/9/21 11:25 PM, Pali Rohár wrote:

[...]

> PCIe Function Level Reset should reset only one PCIe part of device. And
> seems that this type of reset does not work properly in some situations.
> 
> Note that PCIe Function Level Reset is independent of running firmware.
> It is implement in hardware and (should) work also at early stage when
> firmware is not loaded yet.
> 
> I'm starting to think more and more if quirk in this patch really needs
> to be behind DMI check and if rather it should not be called on other
> platforms too?

Maybe? I'm not sure how well this behaves on other devices and if there
even are any devices outside of the MS Surface line that really require
or benefit from something like this. To me it seems safer to put it
behind quirks, at least until we know more.

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.  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.