Re: [Qemu-devel] [RFC PATCH 3/3] acpi: arm: add fw_cfg device node to dsdt

[Igor Mammedov]

On Sat, 12 Sep 2015 19:30:42 -0400
"Gabriel L. Somlo" <address@hidden> wrote:

> Add a fw_cfg device node to the ACPI DSDT. This is mostly
> informational, as the authoritative fw_cfg MMIO region(s)
> are listed in the Device Tree. However, since we are building
> ACPI tables, we might as well be thorough while at it...
> 
> Signed-off-by: Gabriel Somlo <address@hidden>
> ---
> 
> I used surrounding examples to create acpi_dsdt_add_fw_cfg(), and
> noticed that none add a _STA method, and many include a 0 _UID even
> for nodes with a single instance. I wonder whether 1. I really need
> the _UID, and 2. why would we be OK not including a _STA method ?
> 
> Is the #2 answer "because no exisging arm OSPM does in fact check,
> and/or care about the absence of _STA" ? :)
> 
> Thanks,
>  --Gabriel
> 
>  hw/arm/virt-acpi-build.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index 9088248..150c9f9 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -110,6 +110,23 @@ static void acpi_dsdt_add_rtc(Aml *scope, const 
> MemMapEntry *rtc_memmap,
>      aml_append(scope, dev);
>  }
>  
> +static void acpi_dsdt_add_fw_cfg(Aml *scope, const MemMapEntry 
> *fw_cfg_memmap)
> +{
> +    Aml *dev = aml_device("FWCF");
> +    aml_append(dev, aml_name_decl("_HID", aml_string("FWCF0001")));
> +
> +    /* FIXME: is this necessary ? */
in this case you don't need _UID since there is only one instance of given
device.

> +    aml_append(dev, aml_name_decl("_UID", aml_int(0)));
> +    /* FIXME: why doesn't a _STA get added to any other node ? */
> +    aml_append(dev, aml_name_decl("_STA", aml_int(0x0B)));
if _STA is not present OSPM must assume that device is present, that's
why it's not used for always present devices.
0x0B is used to hide given device (usually driver-less) in
Windows's device manager.

> +
> +    Aml *crs = aml_resource_template();
> +    aml_append(crs, aml_memory32_fixed(fw_cfg_memmap->base,
> +                                       fw_cfg_memmap->size, AML_READ_WRITE));
> +    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;
> @@ -519,6 +536,7 @@ build_dsdt(GArray *table_data, GArray *linker, 
> VirtGuestInfo *guest_info)
>                         (irqmap[VIRT_UART] + ARM_SPI_BASE));
>      acpi_dsdt_add_rtc(scope, &memmap[VIRT_RTC],
>                        (irqmap[VIRT_RTC] + ARM_SPI_BASE));
> +    acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]);
>      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);