On Fri, Nov 05, 2021 at 06:33:08PM -0700, Ricardo Neri wrote:
> +static __init int hfi_parse_features(void)
> +{
> + unsigned int nr_capabilities, reg;
> +
> + /*
> + * If we are here we know that CPUID_HFI_LEAF exists. Parse the
> + * supported capabilities and the size of the HFI table.
> + */
> + reg = cpuid_edx(CPUID_HFI_LEAF);
> +
> + hfi_features.capabilities = reg & HFI_CAPABILITIES_MASK;
> + if (!(hfi_features.capabilities & HFI_CAPABILITIES_PERFORMANCE)) {
> + pr_err("Performance reporting not supported! Not using HFI\n");
> + return -ENODEV;
> + }
> +
> + /* The number of 4KB pages required by the table */
> + hfi_features.nr_table_pages = ((reg & CPUID_HFI_TABLE_SIZE_MASK) >>
> + CPUID_HFI_TABLE_SIZE_SHIFT) + 1;
> +
> +/* Hardware Feedback Interface Enumeration */
> +#define CPUID_HFI_LEAF 6
> +#define CPUID_HFI_CAP_MASK 0xff
> +#define CPUID_HFI_TABLE_SIZE_MASK 0x0f00
> +#define CPUID_HFI_TABLE_SIZE_SHIFT 8
> +#define CPUID_HFI_CPU_INDEX_MASK 0xffff0000
Also, *if* you're going to do something like this, then at least write
out the masks in full so you can easily see how they relate. The above
is crap.
> +#define CPUID_HFI_CPU_INDEX_SHIFT 16
> +
> +/* Hardware Feedback Interface Pointer */
> +#define HFI_PTR_VALID_BIT BIT(0)
> +#define HFI_PTR_ADDR_SHIFT 12
> +
> +/* Hardware Feedback Interface Configuration */
> +#define HFI_CONFIG_ENABLE_BIT BIT(0)
> +
> +/* Hardware Feedback Interface Capabilities */
> +#define HFI_CAPABILITIES_MASK 0xff
> +#define HFI_CAPABILITIES_NR 8
> +#define HFI_CAPABILITIES_PERFORMANCE BIT(0)
> +#define HFI_CAPABILITIES_ENERGY_EFF BIT(1)
So personally I prefer a bitfield union a-la cpuid10_eax, cpuid10_ebx
cpuid10_edx etc.. Barring that, the above can also be written more
concise using FIELD_GET() from bitfields.
union cpuid6_edx {
struct {
unsigned int capabilities : 8;
unsigned int table_size : 4;
unsigned int __reserved : 4;
unsigned int cpu_index : 16;
};
unsigned int full;
};
