Re: [Qemu-devel] [PATCH v3] ARM: Virt: Don't generate RTC ACPI device when using UEFI

[Andrew Jones <drjones@redhat.com>]

On Fri, Jan 15, 2016 at 10:11:31PM +0800, Shannon Zhao wrote:
> When booting the VM with UEFI, UEFI takes ownership of the RTC hardware.
> While UEFI can use libfdt to disable the RTC device node in the DTB that
> it passes to the OS, it cannot modify AML. Therefore, we won't generate
> the RTC ACPI device at all when using UEFI.
> 
> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
> ---
> V3: add comments to explain why it doesn't generate RTC ACPI device
> ---
>  hw/arm/virt-acpi-build.c | 24 +++++-------------------
>  1 file changed, 5 insertions(+), 19 deletions(-)
> 
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index 0caf5ce..0d5c635 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -94,23 +94,6 @@ static void acpi_dsdt_add_uart(Aml *scope, const MemMapEntry *uart_memmap,
>      aml_append(scope, dev);
>  }
>  
> -static void acpi_dsdt_add_rtc(Aml *scope, const MemMapEntry *rtc_memmap,
> -                                          uint32_t rtc_irq)
> -{
> -    Aml *dev = aml_device("RTC0");
> -    aml_append(dev, aml_name_decl("_HID", aml_string("LNRO0013")));
> -    aml_append(dev, aml_name_decl("_UID", aml_int(0)));
> -
> -    Aml *crs = aml_resource_template();
> -    aml_append(crs, aml_memory32_fixed(rtc_memmap->base,
> -                                       rtc_memmap->size, AML_READ_WRITE));
> -    aml_append(crs,
> -               aml_interrupt(AML_CONSUMER, AML_LEVEL, AML_ACTIVE_HIGH,
> -                             AML_EXCLUSIVE, &rtc_irq, 1));
> -    aml_append(dev, aml_name_decl("_CRS", crs));
> -    aml_append(scope, dev);
> -}
> -
>  static void acpi_dsdt_add_flash(Aml *scope, const MemMapEntry *flash_memmap)
>  {
>      Aml *dev, *crs;
> @@ -571,12 +554,15 @@ build_dsdt(GArray *table_data, GArray *linker, VirtGuestInfo *guest_info)
>      /* Reserve space for header */
>      acpi_data_push(dsdt->buf, sizeof(AcpiTableHeader));
>  
> +    /* When booting the VM with UEFI, UEFI takes ownership of the RTC hardware.
> +     * While UEFI can use libfdt to disable the RTC device node in the DTB that
> +     * it passes to the OS, it cannot modify AML. Therefore, we won't generate
> +     * the RTC ACPI device at all when using UEFI.
> +     */
>      scope = aml_scope("\\_SB");
>      acpi_dsdt_add_cpus(scope, guest_info->smp_cpus);
>      acpi_dsdt_add_uart(scope, &memmap[VIRT_UART],
>                         (irqmap[VIRT_UART] + ARM_SPI_BASE));
> -    acpi_dsdt_add_rtc(scope, &memmap[VIRT_RTC],
> -                      (irqmap[VIRT_RTC] + ARM_SPI_BASE));
>      acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]);
>      acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO],
>                      (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS);
> -- 
> 2.1.0
> 
>

Reviewed-by: Andrew Jones <drjones@redhat.com>