On Thu, Sep 29, 2022 at 10:09:02PM -0700, Lucas De Marchi wrote: > It's no obviously clear how the encode/decode of the per platform tables This should probably say "...not obvious..." or "...not clear..." Otherwise, Reviewed-by: Matt Roper <matthew.d.roper@xxxxxxxxx> > is done. Document it so while adding tables for new platforms people can > be confident they right things is being done. > > Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx> > --- > drivers/gpu/drm/i915/gt/intel_lrc.c | 24 ++++++++++++++++++++++++ > 1 file changed, 24 insertions(+) > > diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c > index 3515882a91fb..7771a19008c6 100644 > --- a/drivers/gpu/drm/i915/gt/intel_lrc.c > +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c > @@ -20,6 +20,30 @@ > #include "intel_ring.h" > #include "shmem_utils.h" > > +/* > + * The per-platform tables are u8-encoded in @data. Decode @data and set the > + * addresses' offset and commands in @regs. The following encoding is used > + * for each byte. There are 2 steps: decoding commands and decoding addresses. > + * > + * Commands: > + * [7]: create NOPs - number of NOPs are set in lower bits > + * [6]: When creating MI_LOAD_REGISTER_IMM command, allow to set > + * MI_LRI_FORCE_POSTED > + * [5:0]: Number of NOPs or registers to set values to in case of > + * MI_LOAD_REGISTER_IMM > + * > + * Addresses: these are decoded after a MI_LOAD_REGISTER_IMM command by "count" > + * number of registers. They are set by using the REG/REG16 macros: the former > + * is used for offsets smaller than 0x200 while the latter is for values bigger > + * than that. Those macros already set all the bits documented below correctly: > + * > + * [7]: When a register offset needs more than 6 bits, use additional bytes, to > + * follow, for the lower bits > + * [6:0]: Register offset, without considering the engine base. > + * > + * This function only tweaks the commands and register offsets. Values are not > + * filled out. > + */ > static void set_offsets(u32 *regs, > const u8 *data, > const struct intel_engine_cs *engine, > -- > 2.37.3 > -- Matt Roper Graphics Software Engineer VTT-OSGC Platform Enablement Intel Corporation
