On Mon, Jan 21, 2019 at 05:30:00PM +0100, Ard Biesheuvel wrote: > > Until that happens we should just change the driver ifdefs to default > > the hacks to off and only enable them on setups where we 100% > > positively know that they actually work. And document that fact > > in big fat comments. > > Well, as I mentioned in my commit log as well, if we default to off > unless CONFIG_X86, we may break working setups on MIPS and Power where > the device is in fact non-cache coherent, and relies on this > 'optimization' to get things working. The same could be true for > non-coherent ARM systems, hence my approach to disable this hack for > cache coherent devices on non-X86 only. Do we break existing setups or just reduce performance due to the lack of WC mappings? I thought it was the latter. The point is that even your check won't do what you actually said. At lot of non-loongson mips platforms are not cache coherent. As are a lot of arm setups and all sparc64 ones for example. And chances that someone will hacks this file out in a random subsystem when adding news ports also is rather slim, so we'll remaing broken by default. That is why I want at very least: a whitelist instead of a blacklist and some very big comments explaining what is going on here. And in the mid to long term even drm really needs to learn to use the proper APIs :( _______________________________________________ amd-gfx mailing list amd-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/amd-gfx
