[PATCH RFC 0/2] bcma: support for SHIM-attached SoC backplane (BCM6362)

[Alessio Ferri <alessio.ferri@mythread.it>]

This RFC introduces the minimal infrastructure in bcma to support
SoCs that publish a SHIM-style mini-EROM: a backplane on a big-
endian peripheral bus where ChipCommon, the IEEE 802.11 core and
BCMA_CORE_SHIM all report NMW=NSW=0 because clock and reset
gating happens in the SHIM's per-core Control register rather
than in per-core DMP wrappers.

The two patches:

  1/2  bcma: host_soc: support big-endian SoC backplane with
       wrapper-less core synthesis
  2/2  bcma: scan: allow SHIM-style mini-EROM wrapper-less cores

These two are infrastructure-only and don't interfare with
existing SoC: the default brcm,bus-axi compatible
keeps the existing behaviour, and the new code paths gate on 
bus->big_endian and bus->shim_attached, both populated only 
when DT compatible is one of the new SHIM-quirks ones 
(brcm,bcm6362-bus-axi, brcm,bcm63268-bus-axi). I didn't
include the DT bindings YAML for those new compatibles 
from this RFC - the binding design depends on the feedback.

Context: this builds on an earlier design question to the list
that did not draw a response:

  https://lore.kernel.org/linux-wireless/CAHDv23WJLBEp3ETscVT4Z6E5PQfzTDcofxbZ6jAezZNYde7C0w@mail.gmail.com/

The companion b43 series for the same hardware (BCM6362 single-
die N-PHY rev 8 + radio 2057 rev 8) is in review here:

  https://lore.kernel.org/linux-wireless/4581a48e-a6e4-46b1-853f-16db445d6890@mythread.it/

That b43 series stands on its own (b43 dispatcher gaps for a
PHY+radio combination already partially supported in tree). 
This bcma series creates the conditions for b43 to
bind to a BCM6362 d11 core, but does not change anything for any
other b43 user.

Open design questions:

  1. DT bindings for the new compatible strings. I added
     "brcm,bcm6362-bus-axi" and "brcm,bcm63268-bus-axi" as new
     compatibles alongside the existing "brcm,bus-axi", each with
     its own quirks data block. Is it ok?

  2. SHIM peephole base address. The brcm-shim quirks block
     hard-codes shim_base = 0x10007000, which is the address
     used by both BCM6362 and BCM63268 per the OEM SoC map
     headers. I left the hard-coded value in place for the
     RFC since i think it is fixed, but i'm ok to move it 
     to DT if asked.

  3. Accessor set duplication. The BE variants in patch 1/2
     (read16_be / read32_be / write16_be / write32_be /
     aread32_be / awrite32_be) are direct duplicates of the
     existing helpers with the underlying ioread/iowrite calls
     swapped.

  4. The allow-list extension in patch 2/2 (CHIPCOMMON, 80211,
     SHIM) is gated on bus->shim_attached at the point of the
     check.

If this design is acceptable in principle, the follow-up work
that depends on it is:

  - DT bindings YAML for the new compatibles;
  - A SoC-side wlan-shim platform driver to take the BCM6362
    SHIM out of reset before bcma scans it (currently handled by
    an out-of-tree driver during my bring-up; will upstream);
  - A SPROM fallback driver that registers via
    bcma_arch_register_fallback_sprom(), BCM6362 is spromless
  - DT nodes for BCM6362 and BCM63268-class boards under
    arch/mips/boot/dts/brcm/.

Tested on a D-Link DSL-3580L (BCM6362 SoC, single-die N-PHY rev
8 + radio 2057 rev 8). With patches 1-2 applied plus the
out-of-tree wlan-shim driver and SPROM fallback, bcma scan
enumerates the three SHIM-attached cores, b43 binds to the
802.11 core, and the d11 reaches firmware load and PSM run-up.
If asked, i can provide the full dmesg to verify working status.

I also own a NetGear D4220 and some other broadcom routers 
that i plan to bring up after the BCM6362, they are BCM63168 
and BCM63268. 
The shim_base in quirks block already covers BCM63268 per the
OEM SoC map headers, and i expect the same SHIM-attached 
backplane shape for the BCM63168. 
I plan to reuse this infrastructure for their bring up.

Alessio Ferri (2):
  bcma: host_soc: support big-endian SoC backplane with wrapper-less
    core synthesis
  bcma: scan: allow SHIM-style mini-EROM wrapper-less cores

 drivers/bcma/host_soc.c   | 243 +++++++++++++++++++++++++++++++++++++-
 drivers/bcma/scan.c       |  19 ++-
 include/linux/bcma/bcma.h |  10 ++
 3 files changed, 269 insertions(+), 3 deletions(-)

-- 
2.43.0