linux-kernel - Re: [RFC PATCH 3/3] mwifiex: pcie: add reset

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Date:   Sat, 5 Jun 2021 00:26:52 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Jonas Dreßler <verdre@...d.nl>,
        Amitkumar Karwar <amitkarwar@...il.com>,
        Ganapathi Bhat <ganapathi017@...il.com>,
        Sharvari Harisangam <sharvari.harisangam@....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,
        Maximilian Luz <luzmaximilian@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Pali Rohár <pali@...nel.org>
Subject: Re: [RFC PATCH 3/3] mwifiex: pcie: add reset_wsid quirk for Surface 3

On Sat, Jun 5, 2021 at 12:15 AM Bjorn Helgaas <helgaas@...nel.org> wrote:
> On Sat, May 22, 2021 at 03:18:27PM +0200, Jonas Dreßler wrote:
> > From: Tsuchiya Yuto <kitakar@...il.com>
> >
> > This commit adds reset_wsid quirk and uses this quirk for Surface 3 on
> > card reset.
> >
> > To reset mwifiex on Surface 3, it seems that calling the _DSM method
> > exists in \_SB.WSID [1] device is required.
> >
> > On Surface 3, calling the _DSM method removes/re-probes the card by
> > itself. So, need to place the reset function before performing FLR and
> > skip performing any other reset-related works.
>
> Maybe this is a nit-pick, but I understand "probing" to be something
> the OS does, namely what we normally call "enumeration," i.e.,
> discovering a device.
>
> So it sounds like the _DSM causes a logical hot-removal of the card,
> which the PCI hotplug driver should notice and it should remove the
> driver and remove the pci_dev.
>
> And the _DSM also causes a hot-add (reading the code below, it looks
> like this is actually a second _DSM),

_DSM can be only one (single) per device node in ACPI.
But _DSM may have "functions", that's what we see here.

> which the PCI hotplug driver
> should also notice and enumerate the bus (i.e., it reads config space
> looking for a device).  This all would cause a new pci_dev to be
> allocated, resources assigned for its BARs, and the driver .probe()
> method to be called again?
>
> That seems like a lot, so maybe I didn't understand what's actually
> happening.


-- 
With Best Regards,
Andy Shevchenko