Hi Prabhakar, On Thu, Dec 15, 2022 at 12:06 PM Lad, Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote: > On Thu, Dec 15, 2022 at 10:36 AM Geert Uytterhoeven > <geert@xxxxxxxxxxxxxx> wrote: > > On Mon, Dec 12, 2022 at 12:58 PM Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote: > > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx> > > > > > > I/O Coherence Port (IOCP) provides an AXI interface for connecting > > > external non-caching masters, such as DMA controllers. The accesses > > > from IOCP are coherent with D-Caches and L2 Cache. > > > > > > IOCP is a specification option and is disabled on the Renesas RZ/Five > > > SoC due to this reason IP blocks using DMA will fail. > > > > > > The 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. > > > Below are the memory attributes supported: > > > * Device, Non-bufferable > > > * Device, bufferable > > > * Memory, Non-cacheable, Non-bufferable > > > * Memory, Non-cacheable, Bufferable > > > * Memory, Write-back, No-allocate > > > * Memory, Write-back, Read-allocate > > > * Memory, Write-back, Write-allocate > > > * Memory, Write-back, Read and Write-allocate > > > > > > More info about PMA (section 10.3): > > > Link: http://www.andestech.com/wp-content/uploads/AX45MP-1C-Rev.-5.0.0-Datasheet.pdf > > > > > > As a workaround for SoCs with IOCP disabled CMO needs to be handled by > > > software. Firstly OpenSBI configures the memory region as > > > "Memory, Non-cacheable, Bufferable" and passes this region as a global > > > shared dma pool as a DT node. With DMA_GLOBAL_POOL enabled all DMA > > > allocations happen from this region and synchronization callbacks are > > > implemented to synchronize when doing DMA transactions. > > > > > > Example PMA region passes as a DT node from OpenSBI: > > > reserved-memory { > > > #address-cells = <2>; > > > #size-cells = <2>; > > > ranges; > > > > > > pma_resv0@58000000 { > > > compatible = "shared-dma-pool"; > > > reg = <0x0 0x58000000 0x0 0x08000000>; > > > no-map; > > > linux,dma-default; > > > }; > > > }; > > > > > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx> > > > > Thanks for your patch! > > > > > arch/riscv/include/asm/cacheflush.h | 8 + > > > arch/riscv/include/asm/errata_list.h | 28 ++- > > > drivers/soc/renesas/Kconfig | 6 + > > > drivers/soc/renesas/Makefile | 2 + > > > drivers/soc/renesas/rzfive/Kconfig | 6 + > > > drivers/soc/renesas/rzfive/Makefile | 3 + > > > drivers/soc/renesas/rzfive/ax45mp_cache.c | 256 ++++++++++++++++++++++ > > > > Given this touches arch/riscv/include/asm/, I don't think the > > code belongs under drivers/soc/renesas/. > > > Ok. Do you have any suggestions on where you want me to put this code? As it plugs into core riscv functionality, I think it should be under arch/riscv/. if the RISC-V maintainers object to that, another option is drivers/soc/andestech/ or (new) drivers/cache/ Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
