linux-kernel - Re: [RFC PATCH 5/7] riscv: Use pgtable_l4_enabled to output mmu type in cpuinfo

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Date:   Fri, 03 Apr 2020 08:53:15 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     alex@...ti.fr
CC:     Paul Walmsley <paul.walmsley@...ive.com>, zong.li@...ive.com,
        anup@...infault.org, Christoph Hellwig <hch@....de>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        alex@...ti.fr
Subject:     Re: [RFC PATCH 5/7] riscv: Use pgtable_l4_enabled to output mmu type in cpuinfo

On Sun, 22 Mar 2020 04:00:26 PDT (-0700), alex@...ti.fr wrote:
> Now that the mmu type is determined at runtime using SATP
> characteristic, use the global variable pgtable_l4_enabled to output
> mmu type of the processor through /proc/cpuinfo instead of relying on
> device tree infos.
>
> Signed-off-by: Alexandre Ghiti <alex@...ti.fr>
> ---
>  arch/riscv/boot/dts/sifive/fu540-c000.dtsi |  4 ----
>  arch/riscv/kernel/cpu.c                    | 24 ++++++++++++----------
>  2 files changed, 13 insertions(+), 15 deletions(-)
>
> diff --git a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> index 7db861053483..6138590a2229 100644
> --- a/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> +++ b/arch/riscv/boot/dts/sifive/fu540-c000.dtsi
> @@ -50,7 +50,6 @@
>  			i-cache-size = <32768>;
>  			i-tlb-sets = <1>;
>  			i-tlb-size = <32>;
> -			mmu-type = "riscv,sv39";
>  			reg = <1>;
>  			riscv,isa = "rv64imafdc";
>  			tlb-split;
> @@ -74,7 +73,6 @@
>  			i-cache-size = <32768>;
>  			i-tlb-sets = <1>;
>  			i-tlb-size = <32>;
> -			mmu-type = "riscv,sv39";
>  			reg = <2>;
>  			riscv,isa = "rv64imafdc";
>  			tlb-split;
> @@ -98,7 +96,6 @@
>  			i-cache-size = <32768>;
>  			i-tlb-sets = <1>;
>  			i-tlb-size = <32>;
> -			mmu-type = "riscv,sv39";
>  			reg = <3>;
>  			riscv,isa = "rv64imafdc";
>  			tlb-split;
> @@ -122,7 +119,6 @@
>  			i-cache-size = <32768>;
>  			i-tlb-sets = <1>;
>  			i-tlb-size = <32>;
> -			mmu-type = "riscv,sv39";
>  			reg = <4>;
>  			riscv,isa = "rv64imafdc";
>  			tlb-split;
> diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> index 40a3c442ac5f..38a699b997a8 100644
> --- a/arch/riscv/kernel/cpu.c
> +++ b/arch/riscv/kernel/cpu.c
> @@ -8,6 +8,8 @@
>  #include <linux/of.h>
>  #include <asm/smp.h>
>
> +extern bool pgtable_l4_enabled;
> +
>  /*
>   * Returns the hart ID of the given device tree node, or -ENODEV if the node
>   * isn't an enabled and valid RISC-V hart node.
> @@ -54,18 +56,19 @@ static void print_isa(struct seq_file *f, const char *isa)
>  	seq_puts(f, "\n");
>  }
>
> -static void print_mmu(struct seq_file *f, const char *mmu_type)
> +static void print_mmu(struct seq_file *f)
>  {
> +	char sv_type[16];
> +
>  #if defined(CONFIG_32BIT)
> -	if (strcmp(mmu_type, "riscv,sv32") != 0)
> -		return;
> +	strncpy(sv_type, "sv32", 5);
>  #elif defined(CONFIG_64BIT)
> -	if (strcmp(mmu_type, "riscv,sv39") != 0 &&
> -	    strcmp(mmu_type, "riscv,sv48") != 0)
> -		return;
> +	if (pgtable_l4_enabled)
> +		strncpy(sv_type, "sv48", 5);
> +	else
> +		strncpy(sv_type, "sv39", 5);
>  #endif
> -
> -	seq_printf(f, "mmu\t\t: %s\n", mmu_type+6);
> +	seq_printf(f, "mmu\t\t: %s\n", sv_type);
>  }
>
>  static void *c_start(struct seq_file *m, loff_t *pos)
> @@ -90,14 +93,13 @@ static int c_show(struct seq_file *m, void *v)
>  {
>  	unsigned long cpu_id = (unsigned long)v - 1;
>  	struct device_node *node = of_get_cpu_node(cpu_id, NULL);
> -	const char *compat, *isa, *mmu;
> +	const char *compat, *isa;
>
>  	seq_printf(m, "processor\t: %lu\n", cpu_id);
>  	seq_printf(m, "hart\t\t: %lu\n", cpuid_to_hartid_map(cpu_id));
>  	if (!of_property_read_string(node, "riscv,isa", &isa))
>  		print_isa(m, isa);
> -	if (!of_property_read_string(node, "mmu-type", &mmu))
> -		print_mmu(m, mmu);
> +	print_mmu(m);
>  	if (!of_property_read_string(node, "compatible", &compat)
>  	    && strcmp(compat, "riscv"))
>  		seq_printf(m, "uarch\t\t: %s\n", compat);

Reviewed-by: Palmer Dabbelt <palmerdabbelt@...gle.com>