[RFC PATCH v2 0/2] AX45MP: Add support to non-coherent DMA

From: Prabhakar
Date: Mon Oct 03 2022 - 18:32:57 EST

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>

Hi All,

On the Andes AX45MP core, cache coherency is a specification option so it
may not be supported. In this case DMA will fail. To get around with this
issue this patch series does the below:

1] Andes AX45MP core has a Programmable Physical Memory Attributes (PMA)
block that allows dynamic adjustment of memory attributes in the runtime.
It contains a configurable amount of PMA entries implemented as CSR
registers to control the attributes of memory locations in interest. PMA
regions are passed from the l2 node which are configured as
non-cacheable and bufferable with the SBI call.

l2cache: cache-controller@13400000 {
pma-regions = <0x0 0x00000000 0x0 0x14000000>,
<0x0 0x20000000 0x0 0x10000000>,
<0x0 0x58000000 0x0 0x08000000>;

2] We provide callbacks to synchronize specific content between memory and

- arch_sync_dma_for_device()
- arch_sync_dma_for_cpu()

Below are the configs that are enabled:


Below is the L2 cache DT node:

l2cache: cache-controller@13400000 {
compatible = "andestech,ax45mp-cache", "cache";
cache-size = <0x40000>;
cache-line-size = <64>;
cache-sets = <1024>;
reg = <0x0 0x13400000 0x0 0x100000>;
pma-regions = <0x0 0x00000000 0x0 0x10000000>,
<0x0 0x10000000 0x0 0x04000000>,
<0x0 0x20000000 0x0 0x10000000>,
<0x0 0x58000000 0x0 0x08000000>;

Due to the above approach custom SBI calls have been implemented. The
above implementation is in preparation for adding support for Renesas
RZ/Five SoC which uses the AX45MP core. As with the above approach the
kernel image might not be generic so that it can be used on other
platforms, so sending it as an RFC (without DT binding patches).

OpenSBI implementation isn't upstreamed yet, public repo for access is
available at [0].

[0] https://github.com/renesas-rz/rz_opensbi/tree/work/OpenSBI-PMA

RFC v1-> RFC v2
* Moved out the code from arc/riscv to drivers/soc/renesas
* Now handling the PMA setup as part of the L2 cache
* Now making use of dma-noncoherent.c instead SoC specific implementation.
* Dropped arch_dma_alloc() and arch_dma_free()
* Included DT binding doc

RFC v1: https://patchwork.kernel.org/project/linux-renesas-soc/cover/20220906102154.32526-1-prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx/

is used for determining the CMO to call it would better if we could do
this runtime instead.


Lad Prabhakar (2):
dt-bindings: soc: renesas: r9a07g043f-l2-cache: Add DT binding
documentation for L2 cache controller
soc: renesas: Add L2 cache management for RZ/Five SoC

.../soc/renesas/r9a07g043f-l2-cache.yaml | 82 ++++
arch/riscv/include/asm/cacheflush.h | 8 +
arch/riscv/include/asm/errata_list.h | 2 +
arch/riscv/include/asm/sbi.h | 1 +
arch/riscv/mm/dma-noncoherent.c | 20 +
drivers/soc/renesas/Makefile | 4 +
drivers/soc/renesas/rzf/Makefile | 3 +
drivers/soc/renesas/rzf/ax45mp_cache.c | 365 ++++++++++++++++++
drivers/soc/renesas/rzf/rzf_sbi.h | 27 ++
9 files changed, 512 insertions(+)
create mode 100644 Documentation/devicetree/bindings/soc/renesas/r9a07g043f-l2-cache.yaml
create mode 100644 drivers/soc/renesas/rzf/Makefile
create mode 100644 drivers/soc/renesas/rzf/ax45mp_cache.c
create mode 100644 drivers/soc/renesas/rzf/rzf_sbi.h