Re: [PATCH v14 4/5] hw/riscv: virt: Add PMU DT node to the device tree

[Atish Kumar Patra <atishp@rivosinc.com>]

On Mon, Nov 28, 2022 at 12:38 PM <Conor.Dooley@microchip.com> wrote:
>
> On 28/11/2022 20:16, Atish Kumar Patra wrote:
> > On Thu, Nov 24, 2022 at 5:17 AM Conor Dooley <conor.dooley@microchip.com> wrote:
> >>
> >> On Wed, Aug 24, 2022 at 03:17:00PM -0700, Atish Patra wrote:
> >>> 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.
> >>
> >> Hey Atish!
> >>
> >> I was fiddling with dumping the virt machine dtb again today to check
> >> some dt-binding changes I was making for the isa string would play
> >> nicely with the virt machine & I noticed that this patch has introduced
> >> a new validation failure:
> >>
> >> ./build/qemu-system-riscv64 -nographic -machine virt,dumpdtb=qemu.dtb
> >>
> >> dt-validate -p ../linux/Documentation/devicetree/bindings/processed-schema.json qemu.dtb
> >> /home/conor/stuff/qemu/qemu.dtb: soc: pmu: {'riscv,event-to-mhpmcounters': [[1, 1, 524281, 2, 2, 524284, 65561, 65561, 524280, 65563, 65563, 524280, 65569, 65569, 524280, 0, 0, 0, 0, 0]], 'compatible': ['riscv,pmu']} should not be valid under {'type': 'object'}
> >>         From schema: /home/conor/.local/lib/python3.10/site-packages/dtschema/schemas/simple-bus.yaml
> >>
> >> I assume this is the aforementioned "dummy" node & you have no intention
> >> of creating a binding for this?
> >>
> >
> > It is a dummy node from Linux kernel perspective. OpenSbi use this
> > node to figure out the hpmcounter mappings.
>
> Aye, but should it not have a binding anyway, since they're not
> meant to be linux specific?
>
It is documented in OpenSBI.
https://github.com/riscv-software-src/opensbi/blob/master/docs/pmu_support.md

Are you suggesting that any non-Linux specific DT nodes should be part
of Linux DT binding 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>
> >>> ---
> >>>  hw/riscv/virt.c    | 16 +++++++++++++
> >>>  target/riscv/pmu.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++
> >>>  target/riscv/pmu.h |  1 +
> >>>  3 files changed, 74 insertions(+)
> >>>
> >>> diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
> >>> index ff8c0df5cd47..befa9d2c26ac 100644
> >>> --- a/hw/riscv/virt.c
> >>> +++ b/hw/riscv/virt.c
> >>> @@ -30,6 +30,7 @@
> >>>  #include "hw/char/serial.h"
> >>>  #include "target/riscv/cpu.h"
> >>>  #include "hw/core/sysbus-fdt.h"
> >>> +#include "target/riscv/pmu.h"
> >>>  #include "hw/riscv/riscv_hart.h"
> >>>  #include "hw/riscv/virt.h"
> >>>  #include "hw/riscv/boot.h"
> >>> @@ -708,6 +709,20 @@ static void create_fdt_socket_aplic(RISCVVirtState *s,
> >>>      aplic_phandles[socket] = aplic_s_phandle;
> >>>  }
> >>>
> >>> +static void create_fdt_pmu(RISCVVirtState *s)
> >>> +{
> >>> +    char *pmu_name;
> >>> +    MachineState *mc = MACHINE(s);
> >>> +    RISCVCPU hart = s->soc[0].harts[0];
> >>> +
> >>> +    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");
> >>> +    riscv_pmu_generate_fdt_node(mc->fdt, hart.cfg.pmu_num, pmu_name);
> >>> +
> >>> +    g_free(pmu_name);
> >>> +}
> >>> +
> >>>  static void create_fdt_sockets(RISCVVirtState *s, const MemMapEntry *memmap,
> >>>                                 bool is_32_bit, uint32_t *phandle,
> >>>                                 uint32_t *irq_mmio_phandle,
> >>> @@ -1036,6 +1051,7 @@ static void create_fdt(RISCVVirtState *s, const MemMapEntry *memmap,
> >>>
> >>>      create_fdt_flash(s, memmap);
> >>>      create_fdt_fw_cfg(s, memmap);
> >>> +    create_fdt_pmu(s);
> >>>
> >>>  update_bootargs:
> >>>      if (cmdline && *cmdline) {
> >>> diff --git a/target/riscv/pmu.c b/target/riscv/pmu.c
> >>> index a5f504e53c88..b8e56d2b7b8e 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);
> >>> --
> >>> 2.25.1
> >>>
> >>>
> >>>
> >