Re: [PATCH v1 2/3] riscv: cache: Add CBO instructions

[Heinrich Schuchardt <xypron.glpk@gmx.de>]

On 20.08.24 11:37, Mayuresh Chitale wrote:
> Define CBO inval and flush instructions and use those for the
> dcache inval and flush operations respectively.
>
> Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
> ---
>   arch/riscv/Kconfig             |  4 ++
>   arch/riscv/include/asm/cache.h |  3 ++
>   arch/riscv/lib/cache.c         | 90 ++++++++++++++++++++++++++++++++++
>   3 files changed, 97 insertions(+)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index fa3b016c52..0f89d07be7 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -310,6 +310,10 @@ endmenu
>   config RISCV_ISA_A
>   	def_bool y
>
> +config RISCV_ISA_ZICBOM
> +	bool "Zicbom support"
> +	depends on !SYS_DISABLE_DCACHE_OPS
> +
>   config DMA_ADDR_T_64BIT
>   	bool
>   	default y if 64BIT
> diff --git a/arch/riscv/include/asm/cache.h b/arch/riscv/include/asm/cache.h
> index 874963d731..42dbce5b4f 100644
> --- a/arch/riscv/include/asm/cache.h
> +++ b/arch/riscv/include/asm/cache.h
> @@ -9,6 +9,9 @@
>
>   /* cache */
>   void cache_flush(void);
> +void riscv_zicbom_init(void);
> +void cbo_flush(unsigned long start, unsigned long end);
> +void cbo_inval(unsigned long start, unsigned long end);
>
>   /*
>    * The current upper bound for RISCV L1 data cache line sizes is 32 bytes.
> diff --git a/arch/riscv/lib/cache.c b/arch/riscv/lib/cache.c
> index afad7e117f..456353d9c1 100644
> --- a/arch/riscv/lib/cache.c
> +++ b/arch/riscv/lib/cache.c
> @@ -5,6 +5,95 @@
>    */
>
>   #include <cpu_func.h>
> +#include <dm.h>
> +#include <asm/insn-def.h>
> +#include <linux/const.h>
> +
> +#define CBO_INVAL(base)						\
> +	INSN_I(OPCODE_MISC_MEM, FUNC3(2), __RD(0),		\
> +	       RS1(base), SIMM12(0))
> +#define CBO_CLEAN(base)						\
> +	INSN_I(OPCODE_MISC_MEM, FUNC3(2), __RD(0),		\
> +	       RS1(base), SIMM12(1))
> +#define CBO_FLUSH(base)						\
> +	INSN_I(OPCODE_MISC_MEM, FUNC3(2), __RD(0),		\
> +	       RS1(base), SIMM12(2))
> +enum {
> +	CBO_CLEAN,
> +	CBO_FLUSH,
> +	CBO_INVAL
> +} riscv_cbo_ops;
> +static int zicbom_block_size;
> +
> +static inline void do_cbo_clean(unsigned long base)
> +{
> +	asm volatile ("add a0, %0, zero\n" CBO_CLEAN(%0) ::
> +		      "r"(base) : "memory");
> +}
> +
> +static inline void do_cbo_flush(unsigned long base)
> +{
> +	asm volatile ("add a0, %0, zero\n" CBO_FLUSH(%0) ::
> +		      "r"(base) : "memory");
> +}
> +
> +static inline void do_cbo_inval(unsigned long base)
> +{
> +	asm volatile ("add a0, %0, zero\n" CBO_INVAL(%0) ::
> +		      "r"(base) : "memory");
> +}
> +
> +static void cbo_op(int op_type, unsigned long start,
> +		   unsigned long end)
> +{
> +	unsigned long op_size = end - start, size = 0;
> +	void (*fn)(unsigned long base);
> +
> +	switch (op_type) {
> +	case CBO_CLEAN:
> +		fn = do_cbo_clean;
> +		break;
> +	case CBO_FLUSH:
> +		fn = do_cbo_flush;
> +		break;
> +	case CBO_INVAL:
> +		fn = do_cbo_inval;
> +		break;
> +	}
> +	start &= ~(UL(zicbom_block_size - 1));
> +	while (size < op_size) {
> +		fn(start + size);
> +		size += zicbom_block_size;
> +	}
> +}
> +
> +void cbo_flush(unsigned long start, unsigned long end)
> +{
> +	if (zicbom_block_size)
> +		cbo_op(CBO_FLUSH, start, end);
> +}
> +
> +void cbo_inval(unsigned long start, unsigned long end)
> +{
> +	if (zicbom_block_size)
> +		cbo_op(CBO_INVAL, start, end);
> +}
> +
> +void riscv_zicbom_init(void)
> +{
> +	struct udevice *dev;
> +
> +	if (!CONFIG_IS_ENABLED(RISCV_ISA_ZICBOM))
> +		return;
> +
> +	uclass_first_device(UCLASS_CPU, &dev);
> +	if (!dev) {
> +		log_err("Failed to get cpu device!\n");
> +		return;

Please, return an error code.

> +	}
> +
> +	(void)dev_read_u32(dev, "riscv,cbom-block-size", &zicbom_block_size);

Please, do not ignore errors.

Best regards

Heinrich

> +}
>
>   void invalidate_icache_all(void)
>   {
> @@ -72,4 +161,5 @@ __weak int dcache_status(void)
>
>   __weak void enable_caches(void)
>   {
> +	puts("WARNING: Caches not enabled\n");
>   }