Re: [PATCH v3 09/17] ARM64 / ACPI: Parse MADT for SMP initialization

Grant Likely
2014-09-11T10:24:36Z

On Mon, 1 Sep 2014 22:57:47 +0800, Hanjun Guo <hanjun.guo@linaro.org> wrote:
> MADT contains the information for MPIDR which is essential for
> SMP initialization, parse the GIC cpu interface structures to
> get the MPIDR value and map it to cpu_logical_map(), and add
> enabled cpu with valid MPIDR into cpu_possible_map.
>
> ACPI 5.1 only has two explicit methods to boot up SMP, PSCI and
> Parking protocol, but the Parking protocol is only specified for
> ARMv7 now, so make PSCI as the only way for the SMP boot protocol
> before some updates for the ACPI spec or the Parking protocol spec.
>
> Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
> Signed-off-by: Tomasz Nowicki <tomasz.nowicki@linaro.org>
> ---
> +/**
> + * acpi_map_gic_cpu_interface - generates a logical cpu number
> + * and map to MPIDR represented by GICC structure
> + * @mpidr: CPU's hardware id to register, MPIDR represented in MADT
> + * @enabled: this cpu is enabled or not
> + *
> + * Returns the logical cpu number which maps to MPIDR
> + */
> +static int acpi_map_gic_cpu_interface(u64 mpidr, u8 enabled)
> +{
> + int cpu;
> +
> + if (mpidr == INVALID_HWID) {
> + pr_info("Skip invalid cpu hardware ID\n");
> + return -EINVAL;
> + }
> +
> + total_cpus++;
> + if (!enabled)
> + return -EINVAL;
> +
> + if (enabled_cpus >= NR_CPUS) {
> + pr_warn("NR_CPUS limit of %d reached, Processor %d/0x%llx ignored.\n",
> + NR_CPUS, total_cpus, mpidr);
> + return -EINVAL;
> + }
> +
> + /* No need to check duplicate MPIDRs for the first CPU */
> + if (enabled_cpus) {
> + /*
> + * Duplicate MPIDRs are a recipe for disaster. Scan
> + * all initialized entries and check for
> + * duplicates. If any is found just ignore the CPU.
> + */
> + for_each_possible_cpu(cpu) {
> + if (cpu_logical_map(cpu) == mpidr) {
> + pr_err("Firmware bug, duplicate CPU MPIDR: 0x%llx in MADT\n",
> + mpidr);
> + return -EINVAL;
> + }
> + }
> + } else {
> + /* Fist GICC entry must be BSP as ACPI spec said */
> + if (cpu_logical_map(0) != mpidr) {
> + pr_err("First GICC entry is not BSP for MPIDR 0x%llx\n",
> + mpidr);
> + return -EINVAL;
> + }
> + }
> +
> + /* allocate a logical cpu id for the new comer */
> + if (cpu_logical_map(0) == mpidr) {
> + /*
> + * boot_cpu_init() already hold bit 0 in cpu_present_mask
> + * for BSP, no need to allocate again.
> + */
> + cpu = 0;
> + } else {
> + cpu = cpumask_next_zero(-1, cpu_possible_mask);
> + }

Nit: so the above two if/else blocks are essentially testing for the
same condition: Is this the first cpu? or a secondary cpu? I would
merge the two into a single if/else block.

g.