On Thu, Mar 11, 2021 at 9:48 AM Arnd Bergmann [off-list ref] wrote:

On Thu, Mar 11, 2021 at 5:10 PM Rob Herring [off-list ref] wrote:

quoted

On Thu, Mar 11, 2021 at 2:12 AM Arnd Bergmann [off-list ref] wrote:

quoted

On Wed, Mar 10, 2021 at 6:01 PM Rob Herring [off-list ref] wrote:
Ok, makes sense.

Conceptually, I'd like to then see a check that verifies that the
property is only set for nodes whose parent also has it set, since
that is how AXI defines it: A bus can wait for the ack from its
child node, or it can acknowledge the write to its parent early.
However, this breaks down as soon as a bus does the early ack:
all its children by definition use posted writes (as seen by the
CPU), even if they wait for stores that come from other masters.

Does this make sense to you?

BTW, I don't think it's clear in this thread, but the current
definition proposed for the spec[1] and schema is 'nonposted-mmio' is
specific to 'simple-bus'. I like this restriction and we can expand
where 'nonposted-mmio' is allowed later if needed.

That sounds ok, as long as we can express everything for the mac
at the moment. Do we need to explicitly add a description to allow
the property in the root node in addition to simple-bus to be able
to enforce the rule about parent buses also having it?

IMO it should not be allowed in the root node. That's a failure to
define a bus node. Also, would that mean your memory has to be
non-posted!?

Rob