On 08/02/2018 13:26, Chris Wilson wrote:
Quoting Tvrtko Ursulin (2018-02-08 13:05:51)
From: Tvrtko Ursulin <tvrtko.ursu...@intel.com>

For Joonas basically. :)

Rough goal - add Kconfig options to turn off supported platforms and count on
compiler DCE to make the driver smaller.

Tested as so much that it boots and renders on Skylake with all platforms/gens
older than Gen8 turned off.

    text    data     bss     dec     hex filename
1502847   54223    2888 1559958  17cd96 i915.ko.original
1375647   51939    2888 1430474  15d3ca i915.ko.gen8+

So only ~124kiB saving. Or ~8.5%. Perhaps once GCC LTO support lands it would be
better than this?

Did you get to the point where the compiler was complaining about unused
functions?

No, but on a random check it seems that it is removing some. For instance i965_emit_bb_start and i830_emit_bb_start are not in my build.

Doesn't mean I haven't made some other mistake which is preventing more savings.

Starts with smaller patches to show the idea step by step on Gen2, then proceeds
in larger chunks, to finish with some invasive Coccinelle works to enable the
last few kilo-bytes of savings.

So, if we want to support this, how do we test it?

Do a per-platform build and check modinfo for pci ids?

Limit the CI builds to be per-platform and check they work?

Extensively. :) Which will probably be a problem. PCI ids is not enough, I think it would actually need functional testing so a growth of number of builds we would need to test.

Regards,

Tvrtko
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