Re: [PATCH 2/2] hw/riscv/tt-atlantis: Add PRCMs to tt-atlantis model

Hello,

On 7/29/2026 12:21 PM, Anirudh Srinivasan wrote:
> Atlantis has 4 PRCMs that are visible from S mode by the Ascalon Core
> (RCPU, HSIO, PCIe and MM). This commit adds these 4 PRCM blocks to the
> tt-atlantis model, along with necessary device tree nodes for them.
> 
> Signed-off-by: Anirudh Srinivasan <[email protected]>
> ---
>   docs/system/riscv/tt_atlantis.rst |  1 +
>   hw/riscv/tt_atlantis.c            | 92 +++++++++++++++++++++++++++++++++++++++
>   include/hw/riscv/tt_atlantis.h    | 19 ++++++++
>   3 files changed, 112 insertions(+)
> 
> diff --git a/docs/system/riscv/tt_atlantis.rst b/docs/system/riscv/tt_atlantis.rst
> index 1f2880d617..539c22354f 100644
> --- a/docs/system/riscv/tt_atlantis.rst
> +++ b/docs/system/riscv/tt_atlantis.rst
> @@ -14,6 +14,7 @@ tt-atlantis QEMU model features
>   * 8-core Ascalon-X CPU Cluster
>   * RISC-V compliant Advanced Interrupt Architecture
>   * 16550A compatible UART
> +* 4 PRCMs (Clock and Reset Controllers)
>   
>   Known limitations
>   -----------------
> diff --git a/hw/riscv/tt_atlantis.c b/hw/riscv/tt_atlantis.c
> index d808bcc11c..17cc5318b3 100644
> --- a/hw/riscv/tt_atlantis.c
> +++ b/hw/riscv/tt_atlantis.c
> @@ -26,6 +26,7 @@
>   #include "hw/char/serial-mm.h"
>   #include "hw/intc/riscv_aclint.h"
>   #include "hw/misc/unimp.h"
> +#include "hw/misc/tt_atlantis_prcm.h"
>   
>   #include "system/system.h"
>   #include "system/device_tree.h"
> @@ -59,6 +60,10 @@ static const MemMapEntry tt_atlantis_memmap[] = {
>       [TT_ATL_I2C3] =             { 0xd4070000,       0x10000 },
>       [TT_ATL_I2C4] =             { 0xd4080000,       0x10000 },
>       [TT_ATL_UART1] =            { 0xd4110000,       0x10000 },
> +    [TT_ATL_PRCM_RCPU] =        { 0xd0000000,       0x10000 },
> +    [TT_ATL_PRCM_PCIE] =        { 0xd8000000,         0x100 },
> +    [TT_ATL_PRCM_MM] =          { 0xdc000000,        0x1000 },
> +    [TT_ATL_PRCM_HSIO] =        { 0xe00c0000,         0x510 },
>       [TT_ATL_SAPLIC] =           { 0xe8000000,     0x4000000 },
>       [TT_ATL_DDR_HI] =          { 0x100000000,  0x1000000000 },
>   };
> @@ -328,11 +333,38 @@ static void create_fdt_i2c_device(TTAtlantisState *s, int bus,
>       qemu_fdt_setprop_cell(fdt, name, "reg", addr);
>   }
>   
> +static char *create_fdt_prcm(void *fdt, const MemMapEntry *mem,
> +                             const char *prcm_name, uint32_t prcm_phandle)
> +{
> +    hwaddr base = mem->base;
> +    hwaddr size = mem->size;
> +    char *name = g_strdup_printf("/soc/prcm_%s@%" PRIx64,
> +                                 prcm_name, mem->base);
> +    g_autofree char *compatible =
> +        g_strdup_printf("tenstorrent,atlantis-prcm-%s", prcm_name);
> +
> +    qemu_fdt_add_subnode(fdt, name);
> +    qemu_fdt_setprop_string(fdt, name, "compatible", compatible);
> +    qemu_fdt_setprop_sized_cells(fdt, name, "reg", 2, base, 2, size);
> +    qemu_fdt_setprop_cell(fdt, name, "#address-cells", 1);
> +    qemu_fdt_setprop_cell(fdt, name, "#size-cells", 0);
> +    qemu_fdt_setprop_cell(fdt, name, "#clock-cells", 1);
> +    qemu_fdt_setprop_cell(fdt, name, "#reset-cells", 1);
> +    qemu_fdt_setprop_cell(fdt, name, "phandle", prcm_phandle);
> +
> +    return name;
> +}
> +
>   static void finalize_fdt(TTAtlantisState *s)
>   {
>       uint32_t aplic_s_phandle = next_phandle();
>       uint32_t imsic_s_phandle = next_phandle();
>       uint32_t periph_clk_phandle = next_phandle();
> +    uint32_t osc_24m_phandle = next_phandle();
> +    uint32_t prcm_rcpu_phandle = next_phandle();
> +    uint32_t prcm_hsio_phandle = next_phandle();
> +    uint32_t prcm_pcie_phandle = next_phandle();
> +    uint32_t prcm_mm_phandle = next_phandle();

Hmmm seems like you're not really using all of these ... 'osc_24m_phandle'
is indeed needed since you're giving it to create_fdt_clk() and using it
to set "clocks" for all create_fdt_prcm() FDTs.  'prcm_rcpu_phandle' is
also used in other FDTs so it's fine.

But the other 3 phandles aren't used by nothing else aside from supplying
a phandle to create_fdt_prcm().

I think we can make things a little easier by:

- remove the 'uint32_t prcm_phandle' argument from create_fdt_prcm().  When
   creating the phandle do instead:

 > +    qemu_fdt_setprop_cell(fdt, name, "phandle", next_phandle());


-  remove all phandles that you created just to comply with the old create_fdt_prcm().
    Keep osc_24m_phandle as is and just declare  prcm_rcpu_phandle:

 > +    uint32_t osc_24m_phandle = next_phandle();
 > +    uint32_t prcm_rcpu_phandle;


After creating the FDT of rcpu, retrieve the phandle used to create the
rcpu subnode:

 > +    g_autofree char *rcpu_name = create_fdt_prcm(fdt,
 > +        &s->memmap[TT_ATL_PRCM_RCPU], "rcpu");

        prcm_rcpu_phandle = qemu_fdt_get_phandle(fdt, rcpu_name);


And now you have access to the phandles you need for everything, without
bothering storing phandles you don't care about.



Thanks,
Daniel


>       void *fdt = MACHINE(s)->fdt;
>   
>       create_fdt_cpu(s, s->memmap, aplic_s_phandle, imsic_s_phandle);
> @@ -348,6 +380,33 @@ static void finalize_fdt(TTAtlantisState *s)
>                       aplic_s_phandle);
>   
>       create_fdt_clk(fdt, "periph-clk", 100000000, periph_clk_phandle);
> +    create_fdt_clk(fdt, "osc_24m", 24000000, osc_24m_phandle);
> +
> +    g_autofree char *rcpu_name = create_fdt_prcm(fdt,
> +        &s->memmap[TT_ATL_PRCM_RCPU], "rcpu", prcm_rcpu_phandle);
> +    qemu_fdt_setprop_cells(fdt, rcpu_name, "clocks", osc_24m_phandle);
> +    qemu_fdt_setprop_cells(fdt, rcpu_name, "assigned-clocks",
> +                           prcm_rcpu_phandle, TT_ATL_CLK_RCPU_ROOT,
> +                           prcm_rcpu_phandle, TT_ATL_CLK_NOCC_CLK);
> +    qemu_fdt_setprop_cells(fdt, rcpu_name, "assigned-clock-parents",
> +                           prcm_rcpu_phandle, TT_ATL_CLK_RCPU_PLL,
> +                           prcm_rcpu_phandle, TT_ATL_CLK_NOC_PLL);
> +
> +    g_autofree char *hsio_name = create_fdt_prcm(fdt,
> +        &s->memmap[TT_ATL_PRCM_HSIO], "hsio", prcm_hsio_phandle);
> +    qemu_fdt_setprop_cells(fdt, hsio_name, "clocks", osc_24m_phandle,
> +                           prcm_rcpu_phandle, TT_ATL_CLK_HSIO_PLL);
> +
> +    g_autofree char *pcie_name = create_fdt_prcm(fdt,
> +        &s->memmap[TT_ATL_PRCM_PCIE], "pcie", prcm_pcie_phandle);
> +    qemu_fdt_setprop_cells(fdt, pcie_name, "clocks", osc_24m_phandle,
> +                           prcm_rcpu_phandle, TT_ATL_CLK_PCIE_PLL);
> +
> +    g_autofree char *mm_name = create_fdt_prcm(fdt,
> +        &s->memmap[TT_ATL_PRCM_MM], "mm", prcm_mm_phandle);
> +    qemu_fdt_setprop_cells(fdt, mm_name, "clocks", osc_24m_phandle,
> +                           prcm_rcpu_phandle, TT_ATL_CLK_MM_PLL0,
> +                           prcm_rcpu_phandle, TT_ATL_CLK_MM_PLL1);
>   
>       for (int i = 0; i < TT_ATL_NUM_I2C; i++) {
>           create_fdt_i2c(fdt,
> @@ -545,6 +604,39 @@ static void tt_atlantis_machine_init(MachineState *machine)
>       serial_mm_init(system_memory, s->memmap[TT_ATL_UART1].base, 2,
>                      qdev_get_gpio_in(s->irqchip, TT_ATL_UART1_IRQ),
>                      115200, serial_hd(0), DEVICE_LITTLE_ENDIAN);
> +
> +    /* Add rcpu prcm block */
> +    object_initialize_child(OBJECT(s), "prcm-rcpu", &s->prcm[0],
> +                            TYPE_TT_ATLANTIS_PRCM_RCPU);
> +    sysbus_realize(SYS_BUS_DEVICE(&s->prcm[0]), &error_fatal);
> +    memory_region_add_subregion(system_memory,
> +            s->memmap[TT_ATL_PRCM_RCPU].base,
> +            sysbus_mmio_get_region(SYS_BUS_DEVICE(&s->prcm[0]), 0));
> +
> +    /* Add hsio prcm block */
> +    object_initialize_child(OBJECT(s), "prcm-hsio", &s->prcm[1],
> +                            TYPE_TT_ATLANTIS_PRCM_HSIO);
> +    sysbus_realize(SYS_BUS_DEVICE(&s->prcm[1]), &error_fatal);
> +    memory_region_add_subregion(system_memory,
> +            s->memmap[TT_ATL_PRCM_HSIO].base,
> +            sysbus_mmio_get_region(SYS_BUS_DEVICE(&s->prcm[1]), 0));
> +
> +    /* Add pcie prcm block */
> +    object_initialize_child(OBJECT(s), "prcm-pcie", &s->prcm[2],
> +                            TYPE_TT_ATLANTIS_PRCM_PCIE);
> +    sysbus_realize(SYS_BUS_DEVICE(&s->prcm[2]), &error_fatal);
> +    memory_region_add_subregion(system_memory,
> +            s->memmap[TT_ATL_PRCM_PCIE].base,
> +            sysbus_mmio_get_region(SYS_BUS_DEVICE(&s->prcm[2]), 0));
> +
> +    /* Add mm prcm block */
> +    object_initialize_child(OBJECT(s), "prcm-mm", &s->prcm[3],
> +                            TYPE_TT_ATLANTIS_PRCM_MM);
> +    sysbus_realize(SYS_BUS_DEVICE(&s->prcm[3]), &error_fatal);
> +    memory_region_add_subregion(system_memory,
> +            s->memmap[TT_ATL_PRCM_MM].base,
> +            sysbus_mmio_get_region(SYS_BUS_DEVICE(&s->prcm[3]), 0));
> +
>       /*
>        * Atlantis contains a DesignWare uart while the QEMU machine
>        * uses the serial_mm model with the base ns16550 register set.
> diff --git a/include/hw/riscv/tt_atlantis.h b/include/hw/riscv/tt_atlantis.h
> index 7f7d4a5a59..20bcdfeb52 100644
> --- a/include/hw/riscv/tt_atlantis.h
> +++ b/include/hw/riscv/tt_atlantis.h
> @@ -13,12 +13,14 @@
>   #include "hw/core/sysbus.h"
>   #include "hw/i2c/designware_i2c.h"
>   #include "hw/intc/riscv_imsic.h"
> +#include "hw/misc/tt_atlantis_prcm.h"
>   #include "hw/riscv/riscv_hart.h"
>   
>   #define TYPE_TT_ATLANTIS_MACHINE MACHINE_TYPE_NAME("tt-atlantis")
>   OBJECT_DECLARE_SIMPLE_TYPE(TTAtlantisState, TT_ATLANTIS_MACHINE)
>   
>   #define TT_ATL_NUM_I2C 5
> +#define TT_ATL_NUM_PRCM 4
>   
>   struct TTAtlantisState {
>       /*< private >*/
> @@ -31,6 +33,7 @@ struct TTAtlantisState {
>       RISCVHartArrayState soc;
>       DeviceState *irqchip;
>       DesignWareI2CState i2c[TT_ATL_NUM_I2C];
> +    TTAtlantisPRCMState prcm[TT_ATL_NUM_PRCM];
>   
>       int fdt_size;
>   };
> @@ -59,6 +62,22 @@ enum {
>       TT_ATL_SAPLIC,
>       TT_ATL_SIMSIC,
>       TT_ATL_UART1,
> +    TT_ATL_PRCM_RCPU,
> +    TT_ATL_PRCM_HSIO,
> +    TT_ATL_PRCM_PCIE,
> +    TT_ATL_PRCM_MM,
> +};
> +
> +/* RCPU PRCM Clock IDs */
> +enum {
> +    TT_ATL_CLK_RCPU_PLL = 0,
> +    TT_ATL_CLK_RCPU_ROOT = 1,
> +    TT_ATL_CLK_NOC_PLL = 25,
> +    TT_ATL_CLK_NOCC_CLK = 26,
> +    TT_ATL_CLK_HSIO_PLL = 54,
> +    TT_ATL_CLK_PCIE_PLL = 55,
> +    TT_ATL_CLK_MM_PLL0 = 56,
> +    TT_ATL_CLK_MM_PLL1 = 57,
>   };
>   
>   #endif
>