Re: [PATCH V2] hw/loongarch: add rtc acpi table

[chen huacai <zltjiangshi@gmail.com>]

Hi, Xianglai,

On Thu, Mar 12, 2026 at 10:40 AM Xianglai Li <lixianglai@loongson.cn> wrote:
>
> Add the acpi table to the loongson rtc hardware so that the virtual machine
> kernel can use the loongson RTC-related drivers.
>
> Delete the interrupt information in the rtc fdt table.
Why not use virtio-rtc? In this way we don't need to modify the ls7a rtc driver.

Huacai

>
> Signed-off-by: Xianglai Li <lixianglai@loongson.cn>
> ---
> Cc: Song Gao <gaosong@loongson.cn>
> Cc: Bibo Mao <maobibo@loongson.cn>
> Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
>
> change:
> V1->V2:
> 1.Add a comment to explain why the acpi table no longer provides interrupt numbers
> 2.Delete the interrupt number from the rtc fdt table
>
>  hw/loongarch/virt-acpi-build.c | 25 +++++++++++++++++++++++++
>  hw/loongarch/virt-fdt-build.c  | 16 ++++++++--------
>  2 files changed, 33 insertions(+), 8 deletions(-)
>
> diff --git a/hw/loongarch/virt-acpi-build.c b/hw/loongarch/virt-acpi-build.c
> index 3e34bedcd6..42820001d7 100644
> --- a/hw/loongarch/virt-acpi-build.c
> +++ b/hw/loongarch/virt-acpi-build.c
> @@ -460,6 +460,30 @@ static void acpi_dsdt_add_tpm(Aml *scope, LoongArchVirtMachineState *vms)
>  }
>  #endif
>
> +static void acpi_dsdt_add_rtc(Aml *scope)
> +{
> +    Aml *dev = aml_device("RTC");
> +
> +    aml_append(dev, aml_name_decl("_HID", aml_string("LOON0001")));
> +    aml_append(dev, aml_name_decl("_UID", aml_int(0)));
> +
> +    Aml *crs = aml_resource_template();
> +    aml_append(crs,
> +        aml_qword_memory(AML_POS_DECODE, AML_MIN_FIXED, AML_MAX_FIXED,
> +                         AML_NON_CACHEABLE, AML_READ_WRITE,
> +                         0, VIRT_RTC_REG_BASE,
> +                         VIRT_RTC_REG_BASE + VIRT_RTC_LEN - 1,
> +                         0, VIRT_RTC_LEN));
> +    /*
> +     * The virtual machine model does not support suspend and wake-up,
> +     * and rtc is no longer the wake-up source. Therefore, the current
> +     * rtc table no longer provides the rtc alarm interrupt number to
> +     * avoid the software initializing alarm.
> +     */
> +    aml_append(dev, aml_name_decl("_CRS", crs));
> +    aml_append(scope, dev);
> +}
> +
>  /* build DSDT */
>  static void
>  build_dsdt(GArray *table_data, BIOSLinker *linker, MachineState *machine)
> @@ -475,6 +499,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, MachineState *machine)
>      for (i = 0; i < VIRT_UART_COUNT; i++) {
>          build_uart_device_aml(dsdt, i);
>      }
> +    acpi_dsdt_add_rtc(dsdt);
>      build_pci_device_aml(dsdt, lvms);
>      build_la_ged_aml(dsdt, machine);
>      build_flash_aml(dsdt, lvms);
> diff --git a/hw/loongarch/virt-fdt-build.c b/hw/loongarch/virt-fdt-build.c
> index 6c06b36fca..42f014a7bd 100644
> --- a/hw/loongarch/virt-fdt-build.c
> +++ b/hw/loongarch/virt-fdt-build.c
> @@ -458,8 +458,7 @@ static void fdt_add_uart_node(LoongArchVirtMachineState *lvms,
>      g_free(nodename);
>  }
>
> -static void fdt_add_rtc_node(LoongArchVirtMachineState *lvms,
> -                             uint32_t *pch_pic_phandle)
> +static void fdt_add_rtc_node(LoongArchVirtMachineState *lvms)
>  {
>      char *nodename;
>      hwaddr base = VIRT_RTC_REG_BASE;
> @@ -470,12 +469,13 @@ static void fdt_add_rtc_node(LoongArchVirtMachineState *lvms,
>      qemu_fdt_add_subnode(ms->fdt, nodename);
>      qemu_fdt_setprop_string(ms->fdt, nodename, "compatible",
>                              "loongson,ls7a-rtc");
> +    /*
> +     * The virtual machine model does not support suspend and wake-up,
> +     * and rtc is no longer the wake-up source. Therefore, the current
> +     * rtc table no longer provides the rtc alarm interrupt number to
> +     * avoid the software initializing alarm.
> +     */
>      qemu_fdt_setprop_sized_cells(ms->fdt, nodename, "reg", 2, base, 2, size);
> -    qemu_fdt_setprop_cells(ms->fdt, nodename, "interrupts",
> -                           VIRT_RTC_IRQ - VIRT_GSI_BASE ,
> -                           FDT_IRQ_TYPE_LEVEL_HIGH);
> -    qemu_fdt_setprop_cell(ms->fdt, nodename, "interrupt-parent",
> -                          *pch_pic_phandle);
>      g_free(nodename);
>  }
>
> @@ -550,7 +550,7 @@ void virt_fdt_setup(LoongArchVirtMachineState *lvms)
>          fdt_add_uart_node(lvms, &pch_pic_phandle, base, irq, i == 0);
>      }
>
> -    fdt_add_rtc_node(lvms, &pch_pic_phandle);
> +    fdt_add_rtc_node(lvms);
>      fdt_add_ged_reset(lvms);
>      platform_bus_add_all_fdt_nodes(machine->fdt, "/platic",
>                                     VIRT_PLATFORM_BUS_BASEADDRESS,
> --
> 2.39.1
>
>


-- 
Huacai Chen