Re: [PATCH 2/5] kvx: Implement dcache invalidation primitive

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello,

On 01.03.21 16:58, Jules Maselbas wrote:
> From: Yann Sionneau <ysionneau@kalray.eu>
> 
> Signed-off-by: Yann Sionneau <ysionneau@kalray.eu>
> Signed-off-by: Jules Maselbas <jmaselbas@kalray.eu>
> ---
>  arch/kvx/Kconfig             |  1 +
>  arch/kvx/include/asm/cache.h | 13 ++++++++++
>  arch/kvx/lib/Makefile        |  2 +-
>  arch/kvx/lib/cache.c         | 50 ++++++++++++++++++++++++++++++++++++
>  4 files changed, 65 insertions(+), 1 deletion(-)
>  create mode 100644 arch/kvx/lib/cache.c
> 
> diff --git a/arch/kvx/Kconfig b/arch/kvx/Kconfig
> index 8483ae6e6..4e02613ec 100644
> --- a/arch/kvx/Kconfig
> +++ b/arch/kvx/Kconfig
> @@ -12,6 +12,7 @@ config KVX
>  	select FLEXIBLE_BOOTARGS
>  	select GENERIC_FIND_NEXT_BIT
>  	select HAS_ARCH_SJLJ
> +	select HAS_CACHE
>  	select LIBFDT
>  	select MFD_SYSCON
>  	select OF_BAREBOX_DRIVERS
> diff --git a/arch/kvx/include/asm/cache.h b/arch/kvx/include/asm/cache.h
> index 3be176725..efdbcc630 100644
> --- a/arch/kvx/include/asm/cache.h
> +++ b/arch/kvx/include/asm/cache.h
> @@ -15,4 +15,17 @@ static inline void sync_caches_for_execution(void)
>  	__builtin_kvx_barrier();
>  }
>  
> +void kvx_dcache_invalidate_mem_area(uint64_t addr, int size);
> +
> +static inline void sync_dcache_icache(void)
> +{
> +	sync_caches_for_execution();
> +}
> +
> +static inline void dcache_inval(void)
> +{
> +	__builtin_kvx_fence();
> +	__builtin_kvx_dinval();
> +}
> +
>  #endif /* __KVX_CACHE_H */
> diff --git a/arch/kvx/lib/Makefile b/arch/kvx/lib/Makefile
> index cee08b0fa..d271ebccf 100644
> --- a/arch/kvx/lib/Makefile
> +++ b/arch/kvx/lib/Makefile
> @@ -3,4 +3,4 @@
>  # Copyright (C) 2019 Kalray Inc.
>  #
>  
> -obj-y	+= cpuinfo.o board.o dtb.o poweroff.o bootm.o setjmp.o
> +obj-y	+= cpuinfo.o board.o dtb.o poweroff.o bootm.o setjmp.o cache.o
> diff --git a/arch/kvx/lib/cache.c b/arch/kvx/lib/cache.c
> new file mode 100644
> index 000000000..4e128891a
> --- /dev/null
> +++ b/arch/kvx/lib/cache.c
> @@ -0,0 +1,50 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +// SPDX-FileCopyrightText: 2021 Yann Sionneau <ysionneau@kalray.eu>, Kalray Inc.
> +
> +#include <asm/cache.h>
> +
> +#define K1_DCACHE_REFILL         (12)
> +#define K1_DCACHE_HWLOOP         (1)
> +#define K1_DCACHE_REFILL_PERCENT (80)
> +#define K1_DCACHE_LINE_SIZE    (64)
> +#define K1_DCACHE_SIZE (128*1024)
> +
> +void kvx_dcache_invalidate_mem_area(uint64_t addr, int size)
> +{
> +	/* if hwloop iterations cost < _K1_DCACHE_REFILL_PERCENT cache refill,
> +	 * use hwloop, otherwise invalid the whole cache
> +	 */
> +	if (size <
> +	(K1_DCACHE_REFILL_PERCENT * (K1_DCACHE_REFILL * K1_DCACHE_SIZE))
> +			/ (100 * (K1_DCACHE_REFILL + K1_DCACHE_HWLOOP))) {
> +		/* number of lines that must be invalidated */
> +		int invalid_lines = ((addr + size) -
> +					(addr & (~(K1_DCACHE_LINE_SIZE - 1))));
> +
> +		invalid_lines = invalid_lines / K1_DCACHE_LINE_SIZE
> +				+ (0 != (invalid_lines % K1_DCACHE_LINE_SIZE));
> +		if (__builtin_constant_p(invalid_lines) && invalid_lines <= 2) {

Note that currently this will always be false, because of lack of link time
optimization. You could split this away the check into the header and leave the
juicy parts here if you want to have this optimization.

> +			/* when inlining (and doing constant folding),
> +			 *  gcc is able to unroll small loops
> +			 */
> +			int i;
> +
> +			for (i = 0; i < invalid_lines; i++) {
> +				__builtin_kvx_dinvall((void *)(addr
> +						+ i * K1_DCACHE_LINE_SIZE));
> +			}
> +		} else if (invalid_lines > 0) {
> +			__asm__ __volatile__ (
> +				"loopdo %1, 0f\n;;\n"
> +				"dinvall 0[%0]\n"
> +				"addd %0 = %0, %2\n;;\n"
> +				"0:\n"
> +				: "+r"(addr)
> +				: "r" (invalid_lines),
> +				"i" (K1_DCACHE_LINE_SIZE)
> +				: "ls", "le", "lc", "memory");
> +		}
> +	} else {
> +		__builtin_kvx_dinval();
> +	}
> +}
> 

-- 
Pengutronix e.K.                           |                             |
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