The AM64x SoCs have 2 dual-core Arm Cortex-R5F processor (R5FSS)
subsystems/clusters. Both the R5F clusters are present within the
MAIN domain (MAIN_R5FSS0 & MAIN_R5FSS1). Each of these can be
configured at boot time to be either run in a new "Single-CPU" mode
or in an Asymmetric Multi Processing (AMP) fashion in Split-mode.
The mode is restricted to "Single-CPU" on some devices with the
appropriate eFuse bit set, but the most common devices support both
modes. These subsystems have 64 KB each Tightly-Coupled Memory (TCM)
internal memories for each core split between two banks - ATCM and
BTCM (further interleaved into two banks). The TCMs of both Cores
are combined in Single-CPU mode to provide a larger 128 KB of memory.
The other notable difference is that the TCMs are spaced 1 MB apart
on these SoCs unlike the existing SoCs.

Add the DT nodes for both these MAIN domain R5F cluster/subsystems,
the two R5F cores are added as child nodes to each of the corresponding
R5F cluster node. Both the clusters are configured to run in Split mode
by default, with the ATCMs enabled to allow the R5 cores to execute
code from DDR with boot-strapping code from ATCM. The inter-processor
communication between the main A72 cores and these processors is
achieved through shared memory and Mailboxes.

The following firmware names are used by default for these cores, and
can be overridden in a board dts file if desired:
  MAIN R5FSS0 Core0: am64-main-r5f0_0-fw (both in Single-CPU & Split modes)
  MAIN R5FSS0 Core1: am64-main-r5f0_1-fw (needed only in Split mode)
  MAIN R5FSS1 Core0: am64-main-r5f1_0-fw (both in Single-CPU & Split modes)
  MAIN R5FSS1 Core1: am64-main-r5f1_1-fw (needed only in Split mode)

NOTE:
A R5FSS cluster can be configured in "Single-CPU" mode by using a
value of 2 for the "ti,cluster-mode" property. Value of 1 is not
permitted (fails the dtbs_check).
Signed-off-by: Suman Anna <s-anna@ti.com>
Reviewed-by: Praneeth Bajjuri <praneeth@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Link: https://lore.kernel.org/r/20210615195718.15898-2-s-anna@ti.com