Re: [RFC patch 2/4] riscv: Get CPU manufacturer information

[Damien Le Moal <Damien.LeMoal@wdc.com>]

On 2021/03/08 12:59, Vincent Chen wrote:
> Issue 3 SBI calls to get the vendor ID, architecture ID and implementation
> ID early in boot so we only need to take the SBI call overhead once.
> 
> Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
> ---
>  arch/riscv/include/asm/csr.h       |  3 +++
>  arch/riscv/include/asm/hwcap.h     |  6 ++++++
>  arch/riscv/include/asm/processor.h |  2 ++
>  arch/riscv/include/asm/soc.h       |  1 +
>  arch/riscv/kernel/cpufeature.c     | 17 +++++++++++++++++
>  arch/riscv/kernel/setup.c          |  2 ++
>  arch/riscv/kernel/soc.c            |  1 +
>  7 files changed, 32 insertions(+)
> 
> diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
> index caadfc1d7487..87ac65696871 100644
> --- a/arch/riscv/include/asm/csr.h
> +++ b/arch/riscv/include/asm/csr.h
> @@ -115,6 +115,9 @@
>  #define CSR_MIP			0x344
>  #define CSR_PMPCFG0		0x3a0
>  #define CSR_PMPADDR0		0x3b0
> +#define CSR_MVENDORID		0xf11
> +#define CSR_MARCHID		0xf12
> +#define CSR_MIMPID		0xf13
>  #define CSR_MHARTID		0xf14
>  
>  #ifdef CONFIG_RISCV_M_MODE
> diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
> index 5ce50468aff1..b7409487c9d2 100644
> --- a/arch/riscv/include/asm/hwcap.h
> +++ b/arch/riscv/include/asm/hwcap.h
> @@ -44,6 +44,12 @@ bool __riscv_isa_extension_available(const unsigned long *isa_bitmap, int bit);
>  #define riscv_isa_extension_available(isa_bitmap, ext)	\
>  	__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_##ext)
>  
> +struct cpu_manufacturer_info_t {
> +	unsigned long vendor_id;
> +	unsigned long arch_id;
> +	unsigned long imp_id;
> +};
> +
>  #endif
>  
>  #endif /* _ASM_RISCV_HWCAP_H */
> diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
> index 3a240037bde2..4e11a9621d14 100644
> --- a/arch/riscv/include/asm/processor.h
> +++ b/arch/riscv/include/asm/processor.h
> @@ -72,6 +72,8 @@ int riscv_of_parent_hartid(struct device_node *node);
>  
>  extern void riscv_fill_hwcap(void);
>  
> +void riscv_fill_cpu_manufacturer_info(void);
> +
>  #endif /* __ASSEMBLY__ */
>  
>  #endif /* _ASM_RISCV_PROCESSOR_H */
> diff --git a/arch/riscv/include/asm/soc.h b/arch/riscv/include/asm/soc.h
> index f494066051a2..03dee6db404c 100644
> --- a/arch/riscv/include/asm/soc.h
> +++ b/arch/riscv/include/asm/soc.h
> @@ -10,6 +10,7 @@
>  #include <linux/of.h>
>  #include <linux/linkage.h>
>  #include <linux/types.h>
> +#include <asm/hwcap.h>
>  
>  #define SOC_EARLY_INIT_DECLARE(name, compat, fn)			\
>  	static const struct of_device_id __soc_early_init__##name	\
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index ac202f44a670..389162ee19ea 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -12,6 +12,8 @@
>  #include <asm/hwcap.h>
>  #include <asm/smp.h>
>  #include <asm/switch_to.h>
> +#include <asm/sbi.h>
> +#include <asm/csr.h>
>  
>  unsigned long elf_hwcap __read_mostly;
>  
> @@ -22,6 +24,8 @@ static DECLARE_BITMAP(riscv_isa, RISCV_ISA_EXT_MAX) __read_mostly;
>  bool has_fpu __read_mostly;
>  #endif
>  
> +struct cpu_manufacturer_info_t cpu_mfr_info;
> +
>  /**
>   * riscv_isa_extension_base() - Get base extension word
>   *
> @@ -149,3 +153,16 @@ void riscv_fill_hwcap(void)
>  		has_fpu = true;
>  #endif
>  }
> +
> +void riscv_fill_cpu_manufacturer_info(void)
> +{
> +#ifndef CONFIG_RISCV_M_MODE
> +	cpu_mfr_info.vendor_id = sbi_get_vendorid();
> +	cpu_mfr_info.arch_id = sbi_get_archid();
> +	cpu_mfr_info.imp_id = sbi_get_impid();
> +#else
> +	cpu_mfr_info.vendor_id = csr_read(CSR_MVENDORID);
> +	cpu_mfr_info.arch_id = csr_read(CSR_MARCHID);
> +	cpu_mfr_info.imp_id = csr_read(CSR_MIMPID);
> +#endif

Why ? reading the registers will work with M-Mode too. It was there before when
we temporarily had the builtin DTB lookup based on vendor/arch/imp (see defunct
soc_lookup_builtin_dtb() in 5.11).

> +}
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index e85bacff1b50..03621ce9092c 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -278,6 +278,8 @@ void __init setup_arch(char **cmdline_p)
>  #endif
>  
>  	riscv_fill_hwcap();
> +

Nit: I do not think the white libe is really necessary here.

> +	riscv_fill_cpu_manufacturer_info();
>  }
>  
>  static int __init topology_init(void)
> diff --git a/arch/riscv/kernel/soc.c b/arch/riscv/kernel/soc.c
> index a0516172a33c..58f6fd91743a 100644
> --- a/arch/riscv/kernel/soc.c
> +++ b/arch/riscv/kernel/soc.c
> @@ -6,6 +6,7 @@
>  #include <linux/libfdt.h>
>  #include <linux/pgtable.h>
>  #include <asm/soc.h>
> +#include <asm/hwcap.h>

Why is this necessary ?

>  
>  /*
>   * This is called extremly early, before parse_dtb(), to allow initializing
> 


-- 
Damien Le Moal
Western Digital Research

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