netdev - Re: [PATCH 09/34] brcmfmac: pcie: Perform firmware selection for Apple platforms

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Date:   Sun, 2 Jan 2022 06:44:30 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Hector Martin <marcan@...can.st>
Cc:     Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Arend van Spriel <aspriel@...il.com>,
        Franky Lin <franky.lin@...adcom.com>,
        Hante Meuleman <hante.meuleman@...adcom.com>,
        Chi-hsien Lin <chi-hsien.lin@...ineon.com>,
        Wright Feng <wright.feng@...ineon.com>,
        Chung-hsien Hsu <chung-hsien.hsu@...ineon.com>,
        Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Mark Kettenis <kettenis@...nbsd.org>,
        Rafał Miłecki <zajec5@...il.com>,
        Pieter-Paul Giesberts <pieter-paul.giesberts@...adcom.com>,
        Hans de Goede <hdegoede@...hat.com>,
        "John W. Linville" <linville@...driver.com>,
        "Daniel (Deognyoun) Kim" <dekim@...adcom.com>,
        "brian m. carlson" <sandals@...stytoothpaste.net>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, brcm80211-dev-list.pdl@...adcom.com,
        SHA-cyfmac-dev-list@...ineon.com
Subject: Re: [PATCH 09/34] brcmfmac: pcie: Perform firmware selection for
 Apple platforms

On Sun, Dec 26, 2021 at 4:37 PM Hector Martin <marcan@...can.st> wrote:

> On Apple platforms, firmware selection uses the following elements:
>
>   Property         Example   Source
>   ==============   =======   ========================
> * Chip name        4378      Device ID
> * Chip revision    B1        OTP
> * Platform         shikoku   DT (ARM64) or ACPI (x86)
> * Module type      RASP      OTP
> * Module vendor    m         OTP
> * Module version   6.11      OTP
> * Antenna SKU      X3        DT (ARM64) or ??? (x86)
>
> In macOS, these firmwares are stored using filenames in this format
> under /usr/share/firmware/wifi:
>
>     C-4378__s-B1/P-shikoku-X3_M-RASP_V-m__m-6.11.txt
>
> To prepare firmwares for Linux, we rename these to a scheme following
> the existing brcmfmac convention:
>
>     brcmfmac<chip><lower(rev)>-pcie.apple,<platform>-<mod_type>-\
>         <mod_vendor>-<mod_version>-<antenna_sku>.txt
>
> The NVRAM uses all the components, while the firmware and CLM blob only
> use the chip/revision/platform/antenna_sku:
>
>     brcmfmac<chip><lower(rev)>-pcie.apple,<platform>-<antenna_sku>.bin
>
> e.g.
>
>     brcm/brcmfmac4378b1-pcie.apple,shikoku-RASP-m-6.11-X3.txt
>     brcm/brcmfmac4378b1-pcie.apple,shikoku-X3.bin
>
> In addition, since there are over 1000 files in total, many of which are
> symlinks or outright duplicates, we deduplicate and prune the firmware
> tree to reduce firmware filenames to fewer dimensions. For example, the
> shikoku platform (MacBook Air M1 2020) simplifies to just 4 files:
>
>     brcm/brcmfmac4378b1-pcie.apple,shikoku.clm_blob
>     brcm/brcmfmac4378b1-pcie.apple,shikoku.bin
>     brcm/brcmfmac4378b1-pcie.apple,shikoku-RASP-m.txt
>     brcm/brcmfmac4378b1-pcie.apple,shikoku-RASP-u.txt
>
> This reduces the total file count to around 170, of which 75 are
> symlinks and 95 are regular files: 7 firmware blobs, 27 CLM blobs, and
> 61 NVRAM config files. We also slightly process NVRAM files to correct
> some formatting issues and add a missing default macaddr= property.
>
> To handle this, the driver must try the following path formats when
> looking for firmware files:
>
>     brcm/brcmfmac4378b1-pcie.apple,shikoku-RASP-m-6.11-X3.txt
>     brcm/brcmfmac4378b1-pcie.apple,shikoku-RASP-m-6.11.txt
>     brcm/brcmfmac4378b1-pcie.apple,shikoku-RASP-m.txt
>     brcm/brcmfmac4378b1-pcie.apple,shikoku-RASP.txt
>     brcm/brcmfmac4378b1-pcie.apple,shikoku-X3.txt *
>     brcm/brcmfmac4378b1-pcie.apple,shikoku.txt
>
> * Not relevant for NVRAM, only for firmware/CLM.
>
> The chip revision nominally comes from OTP on Apple platforms, but it
> can be mapped to the PCI revision number, so we ignore the OTP revision
> and continue to use the existing PCI revision mechanism to identify chip
> revisions, as the driver already does for other chips. Unfortunately,
> the mapping is not consistent between different chip types, so this has
> to be determined experimentally.
>
> Signed-off-by: Hector Martin <marcan@...can.st>

It's a neat hack, and I don't see anyone doing anything smarter so:
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij