[Intel-gfx] Question about latest skl_dmc_ver1_27.bin and kernel version.

[Rodrigo Vivi]

Hi Paul,

The use of symbolic links was deprecated exactly to avoid this kind of situation
you faced when blindly replacing dmc 1.26 per 1.27. We never tested that kernel
version with that DMC so we don't know what to expect.

As the regular end users concerns they should never touch any firmware and rely
on the distribution to update linux-firmware packages.

You, as the linux distribution OSV, should package linux-firmware from linux-firmware.git
and don't hack it.

If you are sure that you need the new version you should then backport the patch:
https://patchwork.freedesktop.org/series/33568/ on your kernel, instead of renaming
files or using symbolic link.

Thanks,
Rodrigo.

On Mon, Mar 05, 2018 at 04:31:59PM -0500, Paul Knopf wrote:
> I am trying to setup Intel's new open-source iHD driver on a Yocto environment.
> 
> https://software.intel.com/en-us/articles/build-and-debug-open-source-media-stack
> 
> The documentation says that skl_dmc_ver1_27.bin is required. Their documentation updates
> a symlink (skl_dmc_ver1.bin), as if the kernel loads it, but starting at kernel 4.8, it
> stopped loading the symlink and instead loads a specific version of the dmc (see here:
> https://github.com/torvalds/linux/blob/v4.8/drivers/gpu/drm/i915/intel_csr.c#L48). Is the
> Intel documentation accurate? It is confusing because the guide refers to 4.14.16
> specifically, which doesn't use the symlink file skl_dmc_ver1.bin.
> 
> Any ways, I tried replacing skl_dmc_ver1_26.bin with skl_dmc_ver1_27.bin to have the same
> effect, but I got a segfault on boot.
> 
> https://pastebin.com/amW9vDdC
> 
> Should I even bother updating the DMC? Should the iHD driver work on most kernels, even
> with 1_26 version of DMC?
> 
> By the way, this is the kernel I am using (with Yocto).
> 
> https://github.com/intel/linux-intel-lts/tree/4.14/yocto/base/drivers/gpu/drm/i915
> 
> Any help would be greatly appreciated. There is no documentation on this stuff.

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