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From:   Doug Anderson <dianders@chromium.org>
Date:   Thu, 10 Mar 2022 16:27:56 -0800
Message-ID: <CAD=FV=U0Qw-OnKJg8SWk9=e=B0qgqnaTHpuR0cRA0WCmSHSJYQ@mail.gmail.com>
Subject: Re: [PATCH 1/2] ath10k: search for default BDF name provided in DT
To:     Kalle Valo <kvalo@kernel.org>
Cc:     Abhishek Kumar <kuabhs@chromium.org>,
        Rakesh Pillai <pillair@codeaurora.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        ath10k <ath10k@lists.infradead.org>,
        netdev <netdev@vger.kernel.org>
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Hi,

On Thu, Mar 10, 2022 at 2:06 AM Kalle Valo <kvalo@kernel.org> wrote:
>
> Doug Anderson <dianders@chromium.org> writes:
>
> > Hi,
> >
> > On Fri, Jan 7, 2022 at 12:05 PM Abhishek Kumar <kuabhs@chromium.org> wrote:
> >>
> >> There can be cases where the board-2.bin does not contain
> >> any BDF matching the chip-id+board-id+variant combination.
> >> This causes the wlan probe to fail and renders wifi unusable.
> >> For e.g. if the board-2.bin has default BDF as:
> >> bus=snoc,qmi-board-id=67 but for some reason the board-id
> >> on the wlan chip is not programmed and read 0xff as the
> >> default value. In such cases there won't be any matching BDF
> >> because the board-2.bin will be searched with following:
> >> bus=snoc,qmi-board-id=ff
>
> I just checked, in ath10k-firmware WCN3990/hw1.0/board-2.bin we have
> that entry:
>
> BoardNames[1]: 'bus=snoc,qmi-board-id=ff'
>
> >> To address these scenarios, there can be an option to provide
> >> fallback default BDF name in the device tree. If none of the
> >> BDF names match then the board-2.bin file can be searched with
> >> default BDF names assigned in the device tree.
> >>
> >> The default BDF name can be set as:
> >> wifi@a000000 {
> >>         status = "okay";
> >>         qcom,ath10k-default-bdf = "bus=snoc,qmi-board-id=67";
> >
> > Rather than add a new device tree property, wouldn't it be good enough
> > to leverage the existing variant?
>
> I'm not thrilled either adding this to Device Tree, we should keep the
> bindings as simple as possible.
>
> > Right now I think that the board file contains:
> >
> > 'bus=snoc,qmi-board-id=67.bin'
> > 'bus=snoc,qmi-board-id=67,qmi-chip-id=320,variant=GO_LAZOR.bin'
> > 'bus=snoc,qmi-board-id=67,qmi-chip-id=320,variant=GO_POMPOM.bin'
> > 'bus=snoc,qmi-board-id=67,qmi-chip-id=4320,variant=GO_LAZOR.bin'
> > 'bus=snoc,qmi-board-id=67,qmi-chip-id=4320,variant=GO_POMPOM.bin'
> >
> > ...and, on lazor for instance, we have:
> >
> > qcom,ath10k-calibration-variant = "GO_LAZOR";
> >
> > The problem you're trying to solve is that on some early lazor
> > prototype hardware we didn't have the "board-id" programmed we could
> > get back 0xff from the hardware. As I understand it 0xff always means
> > "unprogrammed".
> >
> > It feels like you could just have a special case such that if the
> > hardware reports board ID of 0xff and you don't get a "match" that you
> > could just treat 0xff as a wildcard. That means that you'd see the
> > "variant" in the device tree and pick one of the "GO_LAZOR" entries.
> >
> > Anyway, I guess it's up to the people who spend more time in this file
> > which they'd prefer, but that seems like it'd be simple and wouldn't
> > require a bindings addition...
>
> In ath11k we need something similar for that I have been thinking like
> this:
>
> 'bus=snoc,qmi-board-id=67,qmi-chip-id=320,variant=GO_LAZOR'
>
> 'bus=snoc,qmi-board-id=67,qmi-chip-id=320'
>
> 'bus=snoc,qmi-board-id=67'
>
> 'bus=snoc'
>
> Ie. we drop one attribute at a time and try to find a suitable board
> file. Though I'm not sure if it's possible to find a board file which
> works with many different hardware, but the principle would be at least
> that. Would something like that work in your case?

I'll leave it for Abhishek to comment for sure since he's been the one
actively involved in keeping track of our board-2.bin file. As far as
I know:

* Mostly we need this for pre-production hardware that developers
inside Google and Qualcomm still have sitting around on their desks. I
guess some people are even still using this pre-production hardware to
surf the web?

* In the ideal world, we think that the best calibration would be to
use the board-specific one in these cases. AKA if board_id is 0xff
(unprogrammed) and variant is "GO_LAZOR" then the best solution would
be to use the settings for board id 0x67 and variant "GO_LAZOR". This
_ought_ to be better settings than the default 0xff settings without
the "GO_LAZOR".

* In reality, we're probably OK as long as _some_ reasonable settings
get picked. WiFi might not be super range optimized but at least it
will still come up and work.

-Doug