Il 30/10/25 09:21, Chen-Yu Tsai ha scritto:
On Wed, Oct 29, 2025 at 7:05 PM AngeloGioacchino Del Regno
<[email protected]> wrote:
Il 29/10/25 10:14, Chen-Yu Tsai ha scritto:
On Wed, Oct 15, 2025 at 4:41 PM AngeloGioacchino Del Regno
<[email protected]> wrote:
After a reply on the mailing lists [1] it emerged that the DT
property "firmware-name" should not be relied on because of
possible issues with firmware versions.
For MediaTek SCP, there has never been any firmware version vs
driver version desync issue but, regardless, the firmwares are
always using the same name and they're always located in a path
with a specific pattern.
Instead of unconditionally always relying on the firmware-name
devicetree property to get a path to the SCP FW file, drivers
should construct a name based on what firmware it knows and
what hardware it is running on.
In order to do that, add a `scp_get_default_fw_path()` function
that constructs the path and filename based on two of the infos
that the driver can get:
1. The compatible string with the highest priority (so, the
first one at index 0); and
2. The type of SCP HW - single-core or multi-core.
This means that the default firmware path is generated as:
- Single core SCP: mediatek/(soc_model)/scp.img
for example: mediatek/mt8183/scp.img;
- Multi core SCP: mediatek/(soc_model)/scp_c(core_number).img
for example: mediatek/mt8188/scp_c0.img for Core 0, and
mediatek/mt8188/scp_c1.img for Core 1.
I know this patch has been applied, but this scheme doesn't actually
follow what is already in the linux-firmware repository.
For all the supported platforms, the first core, even for multi core SCP,
already have their firmware uploaded as just "scp.img". Multicore SCP
is seen in MT8195 and MT8188.
The only one that is affected is MT8188, which needs a rename or a symlink in
linux-firmware.
MT8195 is not affected by this change, because the SCP is used as single-core,
hence this code will look for scp.img and not for scp_c0.img.
I guess I can send a followup patch?
The only followup patch that I deem to be necessary is one adding a symlink
or renaming for MT8188's SCP and nothing else.
The firmware was uploaded in March of 2025, and is packaged in Debian
Trixie, and was also backported to Bookworm. Either adding a symlink or
renaming it won't trickle down to users for some time. So this seems
like a possible ABI break, where the ABI is the file name.
Or maybe you don't consider it as such because SCP hasn't been enabled
in the kernel in any release yet?
Please remember that some of those SoCs (including MT8195) allow the SCP to be
configured as *either* single-core *or* dual-core - and usually firmwares for
single-core configurations are not compatible with dual-core ones, because of
the SRAM carveout/usage.
For MT8188, whether the current blob is dual core compatible needs to be
checked. The blob upstreamed to linux-firmware was built locally by
MediaTek engineers and is not what we ship with ChromeOS devices.
The current blob is dual core compatible.
We assisted MediaTek (Moudy) in choosing and validating the SCP firmware for
MT8188, and made sure that it uses only one core, and that doesn't clash with
the second core SRAM.
Cheers,
Angelo
ChenYu
