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The number of DWords should be even when doing ring emits as command sequences require QWord alignment. There was some discussion about the maximum length of the MI_LRI command. Quoting Mika "I did some test with bdw: "The maximum is 128 writes, resulting the 8 bit length field of the command being 0xff, thus following the spec. The 128'th write went through. "Perhaps the max command length is then less in older gens? "Perhaps WARN_ON(x > 128) in MI_LOAD_REGISTER_IMM would be in place but one needs minor tweak to command parser a bit also then. #define I915_MAX_WA_REGS 16 keeps us safe for now atleast." Ville commented that on pre-gen6 the length field seems to be restricted to 0x3f though. So for all cases we should be ok. v2: user LRI variant that can write multiple regs in one go (Damien). We can simply insert one NOP at the end instead of one per register write. Cc: Mika Kuoppala <mika.kuoppala@intel.com> Signed-off-by: Arun Siluvery <arun.siluvery@linux.intel.com> Reviewed-by: Damien Lespiau <damien.lespiau@intel.com> [danvet: Add a summary of the MI_LRI length discussion.] Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> |
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