From: Conor Dooley Date: Mon, 18 Mar 2024 15:16:02 +0000 (+0000) Subject: riscv: don't read riscv, isa in the riscv cpu's get_desc() X-Git-Url: http://git.dujemihanovic.xyz/img/static/gitweb.css?a=commitdiff_plain;h=b90edde70127a824d7aa257c6a633c1a030bfb79;p=u-boot.git riscv: don't read riscv, isa in the riscv cpu's get_desc() cpu_get_desc() for the RISC-V CPU currently reads "riscv,isa" to get the description, but it is no longer a required property and cannot be assummed to always be present, as the new "riscv,isa-extensions" and "riscv,isa-base" properties may be present instead. On RISC-V, cpu_get_desc() has two main uses - firstly providing an informational name for the CPU for smbios or at boot with DISPLAY_CPUINFO etc and secondly it forms the basis of ISA extension detection in supports_extension() as it returns (a portion of) an ISA string. cpu_get_desc() returns a string, which aligned with "riscv,isa" but the new property is a list of strings. Rather than add support for the list of strings property, which would require creating an isa string from "riscv,isa-extensions", modify the RISC-V CPU's implementaion of cpu_get_desc() return the first compatible as the cpu description instead. This may be fine for the informational cases, but it would break extension dtection, given supports_extension() expects cpu_get_desc() to return an ISA string. Call dev_read_string() directly in supports_extension() to get the contents of "riscv,isa" so that extension detection remains functional. As a knock-on affect of this change, extension detection is no longer broken for long ISA strings. Previously if the ISA string exceeded the 32 element array that supports_extension() passed to cpu_get_desc(), it would return ENOSPC and no extensions would be detected. This bug probably had no impact as U-Boot does not currently do anything meaningful with the results of supports_extension() and most SoCs supported by U-Boot don't have anywhere near that complex of an ISA string. The QEMU virt machine's CPUs do however, so extension detection doesn't work there. Signed-off-by: Conor Dooley reviewed-by: Leo Yu-Chi Liang --- diff --git a/arch/riscv/cpu/cpu.c b/arch/riscv/cpu/cpu.c index ecfefa1a02..99083e11df 100644 --- a/arch/riscv/cpu/cpu.c +++ b/arch/riscv/cpu/cpu.c @@ -39,7 +39,7 @@ static inline bool supports_extension(char ext) return csr_read(CSR_MISA) & (1 << (ext - 'a')); #elif CONFIG_CPU struct udevice *dev; - char desc[32]; + const char *isa; int i; uclass_find_first_device(UCLASS_CPU, &dev); @@ -47,12 +47,14 @@ static inline bool supports_extension(char ext) debug("unable to find the RISC-V cpu device\n"); return false; } - if (!cpu_get_desc(dev, desc, sizeof(desc))) { + + isa = dev_read_string(dev, "riscv,isa"); + if (isa) { /* * skip the first 4 characters (rv32|rv64) */ - for (i = 4; i < sizeof(desc); i++) { - switch (desc[i]) { + for (i = 4; i < sizeof(isa); i++) { + switch (isa[i]) { case 's': case 'x': case 'z': @@ -64,7 +66,7 @@ static inline bool supports_extension(char ext) */ return false; default: - if (desc[i] == ext) + if (isa[i] == ext) return true; } } diff --git a/drivers/cpu/riscv_cpu.c b/drivers/cpu/riscv_cpu.c index 5d1026b37d..9b1950efe0 100644 --- a/drivers/cpu/riscv_cpu.c +++ b/drivers/cpu/riscv_cpu.c @@ -21,13 +21,13 @@ DECLARE_GLOBAL_DATA_PTR; static int riscv_cpu_get_desc(const struct udevice *dev, char *buf, int size) { - const char *isa; + const char *cpu; - isa = dev_read_string(dev, "riscv,isa"); - if (size < (strlen(isa) + 1)) + cpu = dev_read_string(dev, "compatible"); + if (size < (strlen(cpu) + 1)) return -ENOSPC; - strcpy(buf, isa); + strcpy(buf, cpu); return 0; }