Hi Horatiu,

On Sat, Sep 26, 2020 at 01:20:02PM +0200, Horatiu Vultur wrote:

To be honest, I don't remember precisely. I will need to setup a board
and see exactly. But from what I remember:
- according to this[1] in chapter 3.8.6, table 71. It says that the full
  entry of IS2 is 384. And this 384 represent a full entry. In this row,
  can be also sub entries like: half entry and quater entries. And each
  entry has 2 bits that describes the entry type. So if you have 2 bits
  for each possible entry then you have 8 bits describing each type. One
  observation is even if you have a full entry each pair of 2 bits
  describing the type needs to be set that is a full entry.

But if I have a single entry per row, I have a single Type-Group value,
so I only need to subtract 2, no?

  Maybe if you have a look at Figure 30, it would be a little bit more
  clear. Even there is a register called VCAP_TG_DAT that information
  is storred internally in the VCAP_ENTRY_DAT.

See, this is what I don't understand. You're saying that the Type-Group
is stored as part of the entry inside the TCAM, even if you're accessing
it through a different set of cache registers? What else is stored in a
TCAM row sub-word? The key + mask + Type-Group are stored in the same
sub-word, I assume?

- so having those in mind, then VCAP_IS2_ENTRY_WIDTH is the full entry
  length - 8 bits. 384 - 8 = 376.

But there are 4 Type-Group (and therefore 4 entries per row) only if the
entries are for quarter keys, am I not correct? And the IS2 code
currently uses half keys. Does this variable need to be set differently
according to the key size?

- then if I remember correctly then VCAP_CONST_ENTRY_WIDTH should be
  384? or 12 if it is counting the words.

Yes, it is 384 and the VCAP core version is 0.

Does it make sense or am I completly off?

So, in simple words, what is the physical significance of
(VCAP_CONST_ENTRY_WIDTH - VCAP_CONST_ENTRY_TG_WIDTH * VCAP_CONST_ENTRY_SWCNT)?
To my understanding, it means the size used by all key+mask entries
within a TCAM row (therefore without the length of Type-Group fields)
when that row contains 4 quarter keys. Divide this number by 2, you get
the length of the key, or the length of the mask, for a single sub-word,
BUT only assuming that quarter keys are used.
So, why does this value have any significance to a driver that is not
using quarter keys?

Am _I_ completely off? This is so confusing.

Thanks,
-Vladimir