netdev - Re: [PATCH v2 1/2] mwifiex: Use non-posted PCI write when setting TX ring write pointer

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Date:   Wed, 22 Sep 2021 16:22:16 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Jonas Dreßler <verdre@...d.nl>
Cc:     Amitkumar Karwar <amitkarwar@...il.com>,
        Ganapathi Bhat <ganapathi017@...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,
        Maximilian Luz <luzmaximilian@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Pali Rohár <pali@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Johannes Berg <johannes@...solutions.net>,
        Brian Norris <briannorris@...omium.org>, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/2] mwifiex: Use non-posted PCI write when setting TX
 ring write pointer

On Wed, Sep 22, 2021 at 02:08:39PM +0200, Jonas Dreßler wrote:
> On 9/22/21 1:17 PM, Andy Shevchenko wrote:
> > On Tue, Sep 14, 2021 at 01:48:12PM +0200, Jonas Dreßler wrote:

...

> > Should it have a Fixes tag?
> > 
> 
> Don't think so, there's the infamous
> (https://bugzilla.kernel.org/show_bug.cgi?id=109681) Bugzilla bug it fixes
> though, I'll mention that in v3.

Good idea, use BugLink tag for that!

...

> Interesting, I haven't noticed that mwifiex_write_reg() always returns 0. So
> are you suggesting to remove that return value and get rid of all the "if
> (mwifiex_write_reg()) {}" checks in a separate commit?

Something like this, yes.

> As for why the dummy read/write functions exist, I have no idea. Looking at
> git history it seems they were always there (only change is that
> mwifiex_read_reg() started to handle read errors with commit
> af05148392f50490c662dccee6c502d9fcba33e2). My bet would be that they were
> created to be consistent with sdio.c which is the oldest supported bus type
> in mwifiex.

It has a check against all ones. Also your another patch mentioned wake up.
Perhaps the purpose is to wake up and return if device was/is in power off mode
(D3hot).

-- 
With Best Regards,
Andy Shevchenko