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Date:   Fri, 20 Nov 2020 13:04:19 -0800
From:   Brian Norris <>
To:     Tsuchiya Yuto <>
Cc:     Amitkumar Karwar <>,
        Ganapathi Bhat <>,
        Xinming Hu <>,
        Kalle Valo <>,
        "David S. Miller" <>,
        Jakub Kicinski <>,
        linux-wireless <>,
        "<>" <>,
        Linux Kernel <>,
        Maximilian Luz <>,
        Andy Shevchenko <>,
Subject: Re: [PATCH 1/3] mwifiex: disable ps_mode explicitly by default instead

On Fri, Oct 30, 2020 at 1:04 AM Tsuchiya Yuto <> wrote:
> On Thu, 2020-10-29 at 11:25 -0700, Brian Norris wrote:
> > For the record, Chrome OS supports plenty of mwifiex systems with 8897
> > (SDIO only) and 8997 (PCIe), with PS enabled, and you're hurting
> > those. Your problem sounds to be exclusively a problem with the PCIe
> > 8897 firmware.
> Actually, I already know that some Chromebooks use these mwifiex cards
> (but not out PCIe-88W8897) because I personally like chromiumos. I'm
> always wondering what is the difference. If the difference is firmware,
> our PCIe-88W8897 firmware should really be fixed instead of this stupid
> series.

PCIe is a very different beast. (For one, it uses DMA and
memory-mapped registers, where SDIO has neither.) It was a very
difficult slog to get PCIe/8997 working reliably for the few
Chromebooks that shipped it, and lots of that work is in firmware. I
would not be surprised if the PCIe-related changes Marvell made for
8997 never fed back into their PCIe-8897 firmware. Or maybe they only
ever launched PCIe-8897 for Windows, and the Windows driver included
workarounds that were never published to their Linux driver. But now
I'm just speculating.

> Yes, I'm sorry that I know this series is just a stupid one but I have to
> send this anyway because this stability issue has not been fixed for a
> long time. I should have added this buglink to every commit as well:
> BugLink:
> If the firmware can't be fixed, I'm afraid I have to go this way. It makes
> no sense to keep enabling power_save for the affected devices if we know
> it's broken.

Condolences and sympathy, seriously. You likely have little chance of
getting the firmware fixed, so without new information (e.g,. other
workarounds?), this is the probably the right way to go.


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