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Message-ID: <CAJF2gTQdjDouYTC9+kq-TdXhQch50p121yq8mTwXsGd6g_TSVA@mail.gmail.com>
Date: Wed, 10 Jul 2024 15:11:27 +0800
From: Guo Ren <guoren@...nel.org>
To: Charlie Jenkins <charlie@...osinc.com>
Cc: Conor Dooley <conor@...nel.org>, Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>, Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
Jisheng Zhang <jszhang@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
Jernej Skrabec <jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>,
Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>, Evan Green <evan@...osinc.com>,
Andy Chiu <andy.chiu@...ive.com>, Jessica Clarke <jrtc27@...c27.com>,
linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-sunxi@...ts.linux.dev,
linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v3 05/13] riscv: vector: Use vlenb from DT for thead
On Thu, Jun 20, 2024 at 7:57 AM Charlie Jenkins <charlie@...osinc.com> wrote:
>
> If thead,vlenb is provided in the device tree, prefer that over reading
> the vlenb csr.
>
> Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
> ---
> arch/riscv/Kconfig.vendor | 13 ++++++++++
> arch/riscv/include/asm/cpufeature.h | 2 ++
> arch/riscv/kernel/cpufeature.c | 48 +++++++++++++++++++++++++++++++++++++
> arch/riscv/kernel/vector.c | 12 +++++++++-
> 4 files changed, 74 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/Kconfig.vendor b/arch/riscv/Kconfig.vendor
> index 9897442bd44f..b096548fe0ff 100644
> --- a/arch/riscv/Kconfig.vendor
> +++ b/arch/riscv/Kconfig.vendor
> @@ -26,6 +26,19 @@ config RISCV_ISA_VENDOR_EXT_THEAD
> extensions. Without this option enabled, T-Head vendor extensions will
> not be detected at boot and their presence not reported to userspace.
>
> + If you don't know what to do here, say Y.
> +
> +config RISCV_ISA_XTHEADVECTOR
> + bool "xtheadvector extension support"
> + depends on RISCV_ISA_VENDOR_EXT_THEAD
> + depends on RISCV_ISA_V
> + depends on FPU
> + default y
> + help
> + Say N here if you want to disable all xtheadvector related procedures
> + in the kernel. This will disable vector for any T-Head board that
> + contains xtheadvector rather than the standard vector.
> +
> If you don't know what to do here, say Y.
> endmenu
>
> diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
> index b029ca72cebc..e0a3164c7a06 100644
> --- a/arch/riscv/include/asm/cpufeature.h
> +++ b/arch/riscv/include/asm/cpufeature.h
> @@ -31,6 +31,8 @@ DECLARE_PER_CPU(struct riscv_cpuinfo, riscv_cpuinfo);
> /* Per-cpu ISA extensions. */
> extern struct riscv_isainfo hart_isa[NR_CPUS];
>
> +extern u32 thead_vlenb_of;
> +
> void riscv_user_isa_enable(void);
>
> #define _RISCV_ISA_EXT_DATA(_name, _id, _subset_exts, _subset_exts_size) { \
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 2107c59575dd..077be4ab1f9a 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -37,6 +37,8 @@ static DECLARE_BITMAP(riscv_isa, RISCV_ISA_EXT_MAX) __read_mostly;
> /* Per-cpu ISA extensions. */
> struct riscv_isainfo hart_isa[NR_CPUS];
>
> +u32 thead_vlenb_of;
> +
> /**
> * riscv_isa_extension_base() - Get base extension word
> *
> @@ -625,6 +627,46 @@ static void __init riscv_fill_vendor_ext_list(int cpu)
> }
> }
>
> +static int has_thead_homogeneous_vlenb(void)
> +{
> + int cpu;
> + u32 prev_vlenb = 0;
> + u32 vlenb;
> +
> + /* Ignore thead,vlenb property if xtheavector is not enabled in the kernel */
> + if (!IS_ENABLED(CONFIG_RISCV_ISA_XTHEADVECTOR))
> + return 0;
> +
> + for_each_possible_cpu(cpu) {
> + struct device_node *cpu_node;
> +
> + cpu_node = of_cpu_device_node_get(cpu);
> + if (!cpu_node) {
> + pr_warn("Unable to find cpu node\n");
> + return -ENOENT;
> + }
> +
> + if (of_property_read_u32(cpu_node, "thead,vlenb", &vlenb)) {
> + of_node_put(cpu_node);
> +
> + if (prev_vlenb)
> + return -ENOENT;
> + continue;
> + }
> +
> + if (prev_vlenb && vlenb != prev_vlenb) {
> + of_node_put(cpu_node);
> + return -ENOENT;
> + }
> +
> + prev_vlenb = vlenb;
> + of_node_put(cpu_node);
> + }
> +
> + thead_vlenb_of = vlenb;
> + return 0;
> +}
> +
> static int __init riscv_fill_hwcap_from_ext_list(unsigned long *isa2hwcap)
> {
> unsigned int cpu;
> @@ -689,6 +731,12 @@ static int __init riscv_fill_hwcap_from_ext_list(unsigned long *isa2hwcap)
> riscv_fill_vendor_ext_list(cpu);
> }
>
> + if (riscv_isa_vendor_extension_available(THEAD_VENDOR_ID, XTHEADVECTOR) &&
> + has_thead_homogeneous_vlenb() < 0) {
> + pr_warn("Unsupported heterogeneous vlenb detected, vector extension disabled.\n");
> + elf_hwcap &= ~COMPAT_HWCAP_ISA_V;
> + }
> +
XTHEADVECTOR is 0.7.1 for old XuanTie processors; we only have
homogeneous vlenb=128 chips.
So:
Acked-by: Guo Ren <guoren@...nel.org>
> if (bitmap_empty(riscv_isa, RISCV_ISA_EXT_MAX))
> return -ENOENT;
>
> diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c
> index 6727d1d3b8f2..3ba2f2432483 100644
> --- a/arch/riscv/kernel/vector.c
> +++ b/arch/riscv/kernel/vector.c
> @@ -33,7 +33,17 @@ int riscv_v_setup_vsize(void)
> {
> unsigned long this_vsize;
>
> - /* There are 32 vector registers with vlenb length. */
> + /*
> + * There are 32 vector registers with vlenb length.
> + *
> + * If the thead,vlenb property was provided by the firmware, use that
> + * instead of probing the CSRs.
> + */
> + if (thead_vlenb_of) {
> + this_vsize = thead_vlenb_of * 32;
> + return 0;
> + }
> +
> riscv_v_enable();
> this_vsize = csr_read(CSR_VLENB) * 32;
> riscv_v_disable();
>
> --
> 2.34.1
>
--
Best Regards
Guo Ren
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