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

[Rob Herring <robh@kernel.org>]

On Wed, Oct 19, 2022 at 11:02:42PM +0100, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> 
> 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@andestech.com> for the Andes AndeStart RISC-V CPU.
> 
> [0] https://lore.kernel.org/lkml/1540982130-28248-1-git-send-email-vincentc@andestech.com/
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> ---
>  arch/riscv/include/asm/cacheflush.h    |   8 +
>  arch/riscv/include/asm/errata_list.h   |   2 +
>  arch/riscv/mm/dma-noncoherent.c        |  20 ++
>  drivers/soc/renesas/Kconfig            |   5 +
>  drivers/soc/renesas/Makefile           |   4 +
>  drivers/soc/renesas/rzf/Kconfig        |   6 +
>  drivers/soc/renesas/rzf/Makefile       |   3 +
>  drivers/soc/renesas/rzf/ax45mp_cache.c | 431 +++++++++++++++++++++++++

How many cache drivers do we have around now? I've seen a few bindings 
go by. I'm guessing it is time to stop putting the drivers in the
drivers/soc/ dumping ground.
 
>  drivers/soc/renesas/rzf/ax45mp_sbi.h   |  29 ++
>  9 files changed, 508 insertions(+)
>  create mode 100644 drivers/soc/renesas/rzf/Kconfig
>  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/ax45mp_sbi.h
> 
> diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h
> index 8a5c246b0a21..40aa790be9a3 100644
> --- a/arch/riscv/include/asm/cacheflush.h
> +++ b/arch/riscv/include/asm/cacheflush.h
> @@ -65,6 +65,14 @@ static inline void riscv_noncoherent_supported(void) {}
>  #define SYS_RISCV_FLUSH_ICACHE_LOCAL 1UL
>  #define SYS_RISCV_FLUSH_ICACHE_ALL   (SYS_RISCV_FLUSH_ICACHE_LOCAL)
>  
> +#ifdef CONFIG_AX45MP_L2_CACHE
> +void ax45mp_cpu_dma_inval_range(void *vaddr, size_t end);
> +void ax45mp_cpu_dma_wb_range(void *vaddr, size_t end);
> +
> +#define ALT_CMO_OP(_op, _start, _size, _cachesize)	\
> +		   _op(_start, _size)
> +#endif
> +
>  #include <asm-generic/cacheflush.h>
>  
>  #endif /* _ASM_RISCV_CACHEFLUSH_H */
> diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h
> index 19a771085781..d9cbf60c3b65 100644
> --- 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
>  
>  #endif
> diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-noncoherent.c
> index b0add983530a..5270acca6766 100644
> --- a/arch/riscv/mm/dma-noncoherent.c
> +++ b/arch/riscv/mm/dma-noncoherent.c
> @@ -24,13 +24,25 @@ void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
>  
>  	switch (dir) {
>  	case DMA_TO_DEVICE:
> +#ifdef CONFIG_ERRATA_THEAD_CMO
>  		ALT_CMO_OP(clean, vaddr, size, riscv_cbom_block_size);
> +#elif CONFIG_AX45MP_L2_CACHE
> +		ALT_CMO_OP(ax45mp_cpu_dma_wb_range, vaddr, size, 0x0);
> +#endif

How do you support more than one platform in a build?

Rob