Re: [RFC PATCH v3 2/2] soc: renesas: Add L2 cache management for RZ/Five SoC

[Geert Uytterhoeven]

Hi Prabhakar,

On Thu, Oct 20, 2022 at 12:02 AM Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
>
> On the AX45MP core, cache coherency is a specification option so it may
> not be supported. In this case DMA will fail. As a workaround, firstly we
> allocate a global dma coherent pool from which DMA allocations are taken
> and marked as non-cacheable + bufferable using the PMA region as specified
> in the device tree. Synchronization callbacks are implemented to
> synchronize when doing DMA transactions.
>
> 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
>
> This patch adds support to configure the memory attributes of the memory
> regions as passed from the l2 cache node and exposes the cache management
> ops.
>
> More info about PMA (section 10.3):
> http://www.andestech.com/wp-content/uploads/AX45MP-1C-Rev.-5.0.0-Datasheet.pdf
>
> This feature is based on the work posted [0] by Vincent Chen
> <vincentc@xxxxxxxxxxxxx> for the Andes AndeStart RISC-V CPU.
>
> [0] https://lore.kernel.org/lkml/1540982130-28248-1-git-send-email-vincentc@xxxxxxxxxxxxx/
>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>

Thanks for your patch!

> --- a/arch/riscv/include/asm/errata_list.h
> +++ b/arch/riscv/include/asm/errata_list.h
> @@ -89,6 +89,7 @@ asm volatile(ALTERNATIVE(                                             \
>  #define ALT_THEAD_PMA(_val)
>  #endif
>
> +#ifdef CONFIG_ERRATA_THEAD_CMO
>  /*
>   * dcache.ipa rs1 (invalidate, physical address)
>   * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
> @@ -143,5 +144,6 @@ asm volatile(ALTERNATIVE_2(                                         \
>         : "a0")
>
>  #endif /* __ASSEMBLY__ */
> +#endif

FTR, the new #endif should be above the old #endif.

I noticed because after rebasing on top of commit 65e9fb081877a18c
("drivers/perf: riscv_pmu_sbi: add support for PMU variant on T-Head
C9xx cores") in riscv/for-next, the build failed because the new
ALT_SBI_PMU_OVERFLOW() definition ended up inside both #endifs,
instead of between.

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