Re: [PATCH 3/4] hw: arm: acpi: add UART clock frequency to SPCR table

[Jonathan Cameron via <qemu-devel@nongnu.org>]

On Fri, 18 Jul 2025 19:20:44 +0300
Vadim Chichikalyuk <chichikalyuk@gmail.com> wrote:

> On the ARM virt machine, there is currently no way to programmatically
> discover the frequency of the UART reference clock solely through the use of
> UEFI/ACPI (without the DTB). The SPCR table can include this information
> as of revision 3.
> 
> Bump the revision to 3 and add the clock frequency of 24 MHz to the table.

Maybe add something on why you aren't just skipping forwards to 4 and filling
in the rest of the stuff?

> 
> Signed-off-by: Vadim Chichikalyuk <chichikalyuk@gmail.com>

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> ---
>  hw/arm/virt-acpi-build.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index b01fc4f8ef..029cbb37f7 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -559,12 +559,13 @@ spcr_setup(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
>          .pci_function = 0,
>          .pci_flags = 0,
>          .pci_segment = 0,
> +        .uart_clk_freq = 24000000, /* 24MHz */
>      };
>      /*
> -     * Passing NULL as the SPCR Table for Revision 2 doesn't support
> +     * Passing NULL as the SPCR Table for Revision 3 doesn't support
>       * NameSpaceString.
>       */
> -    build_spcr(table_data, linker, &serial, 2, vms->oem_id, vms->oem_table_id,
> +    build_spcr(table_data, linker, &serial, 3, vms->oem_id, vms->oem_table_id,
>                 NULL);
>  }
>