[Mesa-dev] [PATCH 02/13] i965: Keep track of whether LRI is allowed in the context struct.

[Chris Wilson]

On Sun, Sep 06, 2015 at 07:48:40PM +0300, Francisco Jerez wrote:
> Chris Wilson <chris at chris-wilson.co.uk> writes:
> 
> > On Sun, Sep 06, 2015 at 07:28:12PM +0300, Francisco Jerez wrote:
> >> Chris Wilson <chris at chris-wilson.co.uk> writes:
> >> 
> >> > On Sun, Sep 06, 2015 at 06:12:40PM +0200, Francisco Jerez wrote:
> >> >> This stores the result of can_do_pipelined_register_writes() in the
> >> >> context struct so we can find out later whether LRI can be used to
> >> >> program the L3 configuration.
> >> >
> >> > LRI are whitelisted by their register. To be generic you must explicitly
> >> > test access to the register you want to modify.
> >> > -Chris
> >> >
> >> AFAIK except for the chicken bits used to enable L3 atomics on HSW
> >> (which is tested explicitly elsewhere, see PATCH 07), all other
> >> registers written to are whitelisted since command parser revision 1 --
> >> I don't think that any released kernel version had the command parser
> >> enabled on Gen7 but any of the required registers blacklisted.
> >
> > At the moment you are not even checking that param. The test is written
> > to be independent of knowledge of  cmdparser internals and by virtue a
> > much stronger test. Use it to your advantage.
> > -Chris
> >
> What advantage do you mean?

Kernel indepencence:

> If the test passes the command parser is
> either enabled (in which case L3 programming will work) or there is no
> actual hardware security (in which case L3 programming will work).  If
> it fails the command parser is disabled and hardware security enabled
> (in which case L3 programming will not work either).

Exactly. Which is why I suggest writing the test in that manner.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre