Re: [PATCH v10 11/12] hw/riscv: virt: Add PMU DT node to the device tree

[Heiko Stübner]

Hi Atish,

Am Dienstag, 21. Juni 2022, 01:16:01 CEST schrieb Atish Patra:
> Qemu virt machine can support few cache events and cycle/instret counters.
> It also supports counter overflow for these events.
> 
> Add a DT node so that OpenSBI/Linux kernel is aware of the virt machine
> capabilities. There are some dummy nodes added for testing as well.
> 
> Acked-by: Alistair Francis <alistair.francis@wdc.com>
> Signed-off-by: Atish Patra <atish.patra@wdc.com>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>
> ---

> +static void create_fdt_socket_pmu(RISCVVirtState *s,
> +                                  int socket, uint32_t *phandle,
> +                                  uint32_t *intc_phandles)
> +{
> +    int cpu;
> +    char *pmu_name;
> +    uint32_t *pmu_cells;
> +    MachineState *mc = MACHINE(s);
> +    RISCVCPU hart = s->soc[socket].harts[0];
> +
> +    pmu_cells = g_new0(uint32_t, s->soc[socket].num_harts * 2);
> +
> +    for (cpu = 0; cpu < s->soc[socket].num_harts; cpu++) {
> +        pmu_cells[cpu * 2 + 0] = cpu_to_be32(intc_phandles[cpu]);
> +        pmu_cells[cpu * 2 + 1] = cpu_to_be32(IRQ_PMU_OVF);
> +    }
> +
> +    pmu_name = g_strdup_printf("/soc/pmu");
> +    qemu_fdt_add_subnode(mc->fdt, pmu_name);
> +    qemu_fdt_setprop_string(mc->fdt, pmu_name, "compatible", "riscv,pmu");

Where is the binding document for this?

As the comment below states the "riscv,event-to-mhpmcounters" property
is opensbi-specific and gets removed in the opensbi stage, but that still
leaves the pmu node in it and from the version I found, Rob wasn't overly
happy with the compatible [0]. Did this get addressed?


Thanks
Heiko


[0] https://lore.kernel.org/all/YXhPqfpXh1VZN07T@robh.at.kernel.org/



> +    riscv_pmu_generate_fdt_node(mc->fdt, hart.cfg.pmu_num, pmu_name);
> +
> +    g_free(pmu_name);
> +    g_free(pmu_cells);
> +}
> +
>  static void create_fdt_sockets(RISCVVirtState *s, const MemMapEntry *memmap,
>                                 bool is_32_bit, uint32_t *phandle,
>                                 uint32_t *irq_mmio_phandle,
> @@ -759,6 +786,7 @@ static void create_fdt_sockets(RISCVVirtState *s, const 
> MemMapEntry *memmap,
>                      &intc_phandles[phandle_pos]);
>              }
>          }
> +        create_fdt_socket_pmu(s, socket, phandle, intc_phandles);
>      }
>  
>      if (s->aia_type == VIRT_AIA_TYPE_APLIC_IMSIC) {
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 7d9e2aca12a9..69bbd9fff4e1 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -1110,6 +1110,7 @@ static void riscv_isa_string_ext(RISCVCPU *cpu, char 
> **isa_str, int max_str_len)
>          ISA_EDATA_ENTRY(zve64f, ext_zve64f),
>          ISA_EDATA_ENTRY(zhinx, ext_zhinx),
>          ISA_EDATA_ENTRY(zhinxmin, ext_zhinxmin),
> +        ISA_EDATA_ENTRY(sscofpmf, ext_sscofpmf),
>          ISA_EDATA_ENTRY(svinval, ext_svinval),
>          ISA_EDATA_ENTRY(svnapot, ext_svnapot),
>          ISA_EDATA_ENTRY(svpbmt, ext_svpbmt),
> diff --git a/target/riscv/pmu.c b/target/riscv/pmu.c
> index 34096941c0ce..59feb3c243dd 100644
> --- a/target/riscv/pmu.c
> +++ b/target/riscv/pmu.c
> @@ -20,11 +20,68 @@
>  #include "cpu.h"
>  #include "pmu.h"
>  #include "sysemu/cpu-timers.h"
> +#include "sysemu/device_tree.h"
>  
>  #define RISCV_TIMEBASE_FREQ 1000000000 /* 1Ghz */
>  #define MAKE_32BIT_MASK(shift, length) \
>          (((uint32_t)(~0UL) >> (32 - (length))) << (shift))
>  
> +/**
> + * To keep it simple, any event can be mapped to any programmable counters in
> + * QEMU. The generic cycle & instruction count events can also be monitored
> + * using programmable counters. In that case, mcycle & minstret must continue
> + * to provide the correct value as well. Heterogeneous PMU per hart is not
> + * supported yet. Thus, number of counters are same across all harts.
> + */
> +void riscv_pmu_generate_fdt_node(void *fdt, int num_ctrs, char *pmu_name)
> +{
> +    uint32_t fdt_event_ctr_map[20] = {};
> +    uint32_t cmask;
> +
> +    /* All the programmable counters can map to any event */
> +    cmask = MAKE_32BIT_MASK(3, num_ctrs);
> +
> +   /**
> +    * The event encoding is specified in the SBI specification
> +    * Event idx is a 20bits wide number encoded as follows:
> +    * event_idx[19:16] = type
> +    * event_idx[15:0] = code
> +    * The code field in cache events are encoded as follows:
> +    * event_idx.code[15:3] = cache_id
> +    * event_idx.code[2:1] = op_id
> +    * event_idx.code[0:0] = result_id
> +    */
> +
> +   /* SBI_PMU_HW_CPU_CYCLES: 0x01 : type(0x00) */
> +   fdt_event_ctr_map[0] = cpu_to_be32(0x00000001);
> +   fdt_event_ctr_map[1] = cpu_to_be32(0x00000001);
> +   fdt_event_ctr_map[2] = cpu_to_be32(cmask | 1 << 0);
> +
> +   /* SBI_PMU_HW_INSTRUCTIONS: 0x02 : type(0x00) */
> +   fdt_event_ctr_map[3] = cpu_to_be32(0x00000002);
> +   fdt_event_ctr_map[4] = cpu_to_be32(0x00000002);
> +   fdt_event_ctr_map[5] = cpu_to_be32(cmask | 1 << 2);
> +
> +   /* SBI_PMU_HW_CACHE_DTLB : 0x03 READ : 0x00 MISS : 0x00 type(0x01) */
> +   fdt_event_ctr_map[6] = cpu_to_be32(0x00010019);
> +   fdt_event_ctr_map[7] = cpu_to_be32(0x00010019);
> +   fdt_event_ctr_map[8] = cpu_to_be32(cmask);
> +
> +   /* SBI_PMU_HW_CACHE_DTLB : 0x03 WRITE : 0x01 MISS : 0x00 type(0x01) */
> +   fdt_event_ctr_map[9] = cpu_to_be32(0x0001001B);
> +   fdt_event_ctr_map[10] = cpu_to_be32(0x0001001B);
> +   fdt_event_ctr_map[11] = cpu_to_be32(cmask);
> +
> +   /* SBI_PMU_HW_CACHE_ITLB : 0x04 READ : 0x00 MISS : 0x00 type(0x01) */
> +   fdt_event_ctr_map[12] = cpu_to_be32(0x00010021);
> +   fdt_event_ctr_map[13] = cpu_to_be32(0x00010021);
> +   fdt_event_ctr_map[14] = cpu_to_be32(cmask);
> +
> +   /* This a OpenSBI specific DT property documented in OpenSBI docs */
> +   qemu_fdt_setprop(fdt, pmu_name, "riscv,event-to-mhpmcounters",
> +                    fdt_event_ctr_map, sizeof(fdt_event_ctr_map));
> +}
> +
>  static bool riscv_pmu_counter_valid(RISCVCPU *cpu, uint32_t ctr_idx)
>  {
>      if (ctr_idx < 3 || ctr_idx >= RV_MAX_MHPMCOUNTERS ||
> diff --git a/target/riscv/pmu.h b/target/riscv/pmu.h
> index 036653627f78..3004ce37b636 100644
> --- a/target/riscv/pmu.h
> +++ b/target/riscv/pmu.h
> @@ -31,5 +31,6 @@ int riscv_pmu_init(RISCVCPU *cpu, int num_counters);
>  int riscv_pmu_update_event_map(CPURISCVState *env, uint64_t value,
>                                 uint32_t ctr_idx);
>  int riscv_pmu_incr_ctr(RISCVCPU *cpu, enum riscv_pmu_event_idx event_idx);
> +void riscv_pmu_generate_fdt_node(void *fdt, int num_counters, char 
> *pmu_name);
>  int riscv_pmu_setup_timer(CPURISCVState *env, uint64_t value,
>                            uint32_t ctr_idx);
>