[PATCH v3 0/6] bus/memory: Add Baikal-T1 SoC APB/AXI/L2 drivers

[Serge Semin]

Baikal-T1 SoC CPU is based on two MIPS Warrior P5600 cores. Their main
memory Non-Coherent IO interface is connected to the OCP2AXI bridge, which
in turn is then connected to the DW AMBA 3 AXI Interconnect (so called
Main Interconnect) with nine masters and four slaves ports. Main
Interconnect is responsible for the AXI-bus traffic arbitration (QoS) and
its routing from one component to another. In addition there is a Errors
Handler Block (EHB) accesible by means of the Baikal-T1 SoC System
Controller responsible to detect AXI protocol errors and device not
responding situations built on top the interconnect. Baikal-T1 AXI-bus
driver included in this patchset will be responsible for working with that
functionality, though currently it doesn't support QoS tuning. Instead
it's capable of detecting the error events, reporting an info about them
to the system log, injecting artificial errors to test the driver
functionality. Since AXI Interconnect doesn't provide a way to find out
which devices are connected to it, so its DT node is supposed to be
compatible with "simple-bus" driver, while sub-nodes shall represent the
masters attached to the bus.

One of the AXI Interconnect slaves is an AXI-APB bridge used to access the
Baikal-T1 SoC subsystems CSRs. MMIO request from CPU and DMAC masters are
routed there if they are detected to be within [0x08000000 0x1FFFFFFF]
range of the physical memory. In case if an attempted APB transaction
stays with no response for a pre-defined time it will be detected by the
APB-bus Errors Handler Block (EHB), which will raise an interrupt, then
the bus gets freed for a next operation. The APB-bus driver provides the
interrupt handler to detect the erroneous address, update an errors
counter and prints an error message about the faulty address. The counter
and the APB-bus operations timeout can be accessed via corresponding sysfs
nodes. A dedicated sysfs-node can be also used to artificially cause the
bus errors described above. Since APB-bus is a platform bus, it doesn't
provide a way to detect slave devices connected to it, so similarly to the
AXI-bus it's also supposed to be compatible with "simple-bus" driver.

Aside from PCIe/SATA/DDR/I2C/EHB/CPU/reboot specific settings the
Baikal-T1 System Controller provides a MIPS P5600 CM2 L2-cache tuning
block. It is responsible for the setting up the Tag/Data/WS L2-to-RAM
latencies. The last small patch in this patchset provides a driver and
DT-schema-based binding for the described device. So that the latencies
can be tuned up by means of dedicated DT properties and sysfs nodes.

This patchset is rebased and tested on the mainline Linux kernel 5.7-rc4:
0e698dfa2822 ("Linux 5.7-rc4")
tag: v5.7-rc4

Changelog v2 (AXI/APB bus):
- Assign dual GPL/BSD licenses to the bindings.
- Use single lined copyright headers in the bindings.
- Replace "additionalProperties: false" property with
  "unevaluatedProperties: false" in the bindings.
- Don't use a multi-arg clock phandle reference in DT binding examples.
  Thus remove includes from there.
- Fix some commit message and Kconfig help text spelling.
- Move drivers from soc to the bus subsystem.
- Convert a simple EHB drivers to the Baikal-T1 AXI and APB bus ones.
- Convert APB bus driver to using regmap MMIO API.
- Use syscon regmap to access the AXI-bus erroneous address.
- Add reset line support.
- Add Main Interconnect clock support to the AXI-bus driver.
- Remove probe-status info string printout.
- Discard of_match_ptr() macro utilization.
- Don't print error-message if no platform IRQ found. Just return an error.
- Use generic FIELD_{GET,PREP} macros instead of handwritten ones in the
  AXI-bus driver.

Changelog v2 (l2 driver):
- Fix some commit message and Kconfig help text spelling.
- Move the driver to the memory subsystem.
- Assign dual GPL/BSD license to the DT binding.
- Use single lined copyright header in the binding.
- Discard reg property and syscon compatible string.
- Move "allOf" restrictions to the root level of the properties.
- The DT node is supposed to be a child of the Baikal-T1 system controller
  node. So regmap will be fetched from there.
- Use generic FIELD_{GET,PREP} macro.
- Remove probe-status info string printout.
- Since the driver depends on the OF config we can remove of_match_ptr()
  macro utilization.

Changelog v3:
- Combine l2 and AXI/APB bus patches in a single patchset.
- Retrieve AXI-bus QoS registers by resource name "qos".
- Discard CONFIG_OF dependency since there is none at compile-time.
- Add syscon EHB registers range to the AXI-bus reg property as optional
  entry.
- Fix invalid of_property_read_u32() return value test in the l2-ctl
  driver.
- Get the reg property back into the l2-ctl DT bindings even though the
  driver is using the parental syscon regmap.
- The l2-ctl DT schema will live separately from the system controller,
  but the corresponding sub-node of the later DT schema will $ref this one.
- Set non-default latencies in the l2-ctl DT example.

Signed-off-by: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx>
Cc: Alexey Malahov <Alexey.Malahov@xxxxxxxxxxxxxxxxxxxx>
Cc: Maxim Kaurkin <Maxim.Kaurkin@xxxxxxxxxxxxxxxxxxxx>
Cc: Pavel Parkhomenko <Pavel.Parkhomenko@xxxxxxxxxxxxxxxxxxxx>
Cc: Ramil Zaripov <Ramil.Zaripov@xxxxxxxxxxxxxxxxxxxx>
Cc: Ekaterina Skachko <Ekaterina.Skachko@xxxxxxxxxxxxxxxxxxxx>
Cc: Vadim Vlasov <V.Vlasov@xxxxxxxxxxxxxxxxxxxx>
Cc: Alexey Kolotnikov <Alexey.Kolotnikov@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul Burton <paulburton@xxxxxxxxxx>
Cc: Rob Herring <robh+dt@xxxxxxxxxx>
Cc: Olof Johansson <olof@xxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxxx
Cc: soc@xxxxxxxxxx
Cc: devicetree@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx

Serge Semin (6):
  dt-bindings: bus: Add Baikal-T1 AXI-bus binding
  dt-bindings: bus: Add Baikal-T1 APB-bus binding
  dt-bindings: memory: Add Baikal-T1 L2-cache Control Block binding
  bus: Add Baikal-T1 AXI-bus driver
  bus: Add Baikal-T1 APB-bus driver
  memory: Add Baikal-T1 L2-cache Control Block driver

 .../bindings/bus/baikal,bt1-apb.yaml          |  90 ++++
 .../bindings/bus/baikal,bt1-axi.yaml          | 107 +++++
 .../memory-controllers/baikal,bt1-l2-ctl.yaml |  63 +++
 drivers/bus/Kconfig                           |  30 ++
 drivers/bus/Makefile                          |   2 +
 drivers/bus/bt1-apb.c                         | 421 ++++++++++++++++++
 drivers/bus/bt1-axi.c                         | 318 +++++++++++++
 drivers/memory/Kconfig                        |  11 +
 drivers/memory/Makefile                       |   1 +
 drivers/memory/bt1-l2-ctl.c                   | 322 ++++++++++++++
 10 files changed, 1365 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/bus/baikal,bt1-apb.yaml
 create mode 100644 Documentation/devicetree/bindings/bus/baikal,bt1-axi.yaml
 create mode 100644 Documentation/devicetree/bindings/memory-controllers/baikal,bt1-l2-ctl.yaml
 create mode 100644 drivers/bus/bt1-apb.c
 create mode 100644 drivers/bus/bt1-axi.c
 create mode 100644 drivers/memory/bt1-l2-ctl.c

-- 
2.26.2