Re: [PATCH v3 2/3] hw/arm/virt_acpi_build: Generate DBG2 table

[Andrew Jones]

On Mon, Sep 27, 2021 at 03:17:31PM +0200, Eric Auger wrote:
> ARM SBBR specification mandates DBG2 table (Debug Port Table 2)
> since v1.0 (ARM DEN0044F 8.3.1.7 DBG2).
> 
> The DBG2 table allows to describe one or more debug ports.
> 
> Generate an DBG2 table featuring a single debug port, the PL011.
> 
> The DBG2 specification can be found at
> "Microsoft Debug Port Table 2 (DBG2)"
> https://docs.microsoft.com/en-us/windows-hardware/drivers/bringup/acpi-debug-port-table?redirectedfrom=MSDN
> 
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> 
> ---
> 
> v2 -> v3:
> Took into account all comments from Igor on v2:
> mostly style adjustment, revision references
> 
> v1 -> v2:
> - rebased on Igor's refactoring
> ---
>  hw/arm/virt-acpi-build.c | 62 +++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 61 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index 6cec97352b..257d0fee17 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -616,6 +616,63 @@ build_gtdt(GArray *table_data, BIOSLinker *linker, 
> VirtMachineState *vms)
>      acpi_table_end(linker, &table);
>  }
>  
> +/* Debug Port Table 2 (DBG2) */
> +static void
> +build_dbg2(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)

nit: I didn't think QEMU liked this style, i.e. QEMU prefers

 static void build_dbg2(GArray *table_data, BIOSLinker *linker,
                        VirtMachineState *vms)

Eh, I see that hw/arm/virt-acpi-build.c is full of the format you have
here, so never mind.

> +{
> +    AcpiTable table = { .sig = "DBG2", .rev = 3, .oem_id = vms->oem_id,

Can you explain where the .rev = 3 comes from? The spec says "For this
version of the specification, this value is 0."


> +                        .oem_table_id = vms->oem_table_id };
> +    int dbg2devicelength;
> +    const char name[] = "COM0";
> +    const int namespace_length = sizeof(name);
> +
> +    acpi_table_begin(&table, table_data);
> +
> +    dbg2devicelength = 22 /* BaseAddressRegister[] offset */ +
> +                       12 /* BaseAddressRegister[] */ +
> +                       4 /* AddressSize[] */ +

I'd personally prefer the '+' before the comment, but maybe Igor has a
special ACPI code format preference here.

> +                       namespace_length /* NamespaceString[] */;
> +
> +    /* OffsetDbgDeviceInfo */
> +    build_append_int_noprefix(table_data, 44, 4);
> +    /* NumberDbgDeviceInfo */
> +    build_append_int_noprefix(table_data, 1, 4);
> +
> +    /* Table 2. Debug Device Information structure format */
> +    build_append_int_noprefix(table_data, 0, 1); /* Revision */
> +    build_append_int_noprefix(table_data, dbg2devicelength, 2); /* Length */
> +    /* NumberofGenericAddressRegisters */
> +    build_append_int_noprefix(table_data, 1, 1);
> +    /* NameSpaceStringLength */
> +    build_append_int_noprefix(table_data, namespace_length, 2);
> +    build_append_int_noprefix(table_data, 38, 2); /* NameSpaceStringOffset */
> +    build_append_int_noprefix(table_data, 0, 2); /* OemDataLength */
> +    /* OemDataOffset (0 means no OEM data) */
> +    build_append_int_noprefix(table_data, 0, 2);
> +
> +    /* Port Type */
> +    build_append_int_noprefix(table_data, 0x8000 /* Serial */, 2);
> +    /* Port Subtype */
> +    build_append_int_noprefix(table_data, 0x3 /* ARM PL011 UART */, 2);
> +    build_append_int_noprefix(table_data, 0, 2); /* Reserved */
> +    /* BaseAddressRegisterOffset */
> +    build_append_int_noprefix(table_data, 22, 2);
> +    /* AddressSizeOffset */
> +    build_append_int_noprefix(table_data, 34, 2);
> +
> +    /* BaseAddressRegister[] */
> +    build_append_gas(table_data, AML_AS_SYSTEM_MEMORY, 8, 0, 1,
> +                     vms->memmap[VIRT_UART].base);
> +
> +    /* AddressSize[] */
> +    build_append_int_noprefix(table_data, 0x1000 /* Register Space */, 4);
> +
> +    /* NamespaceString[] */
> +    g_array_append_vals(table_data, name, namespace_length);
> +
> +    acpi_table_end(linker, &table);
> +};
> +
>  /*
>   * ACPI spec, Revision 5.1 Errata A
>   * 5.2.12 Multiple APIC Description Table (MADT)
> @@ -875,7 +932,7 @@ void virt_acpi_build(VirtMachineState *vms, 
> AcpiBuildTables *tables)
>      dsdt = tables_blob->len;
>      build_dsdt(tables_blob, tables->linker, vms);
>  
> -    /* FADT MADT GTDT MCFG SPCR pointed to by RSDT */
> +    /* FADT MADT GTDT MCFG SPCR DBG2 pointed to by RSDT */
>      acpi_add_table(table_offsets, tables_blob);
>      build_fadt_rev5(tables_blob, tables->linker, vms, dsdt);
>  
> @@ -898,6 +955,9 @@ void virt_acpi_build(VirtMachineState *vms, 
> AcpiBuildTables *tables)
>      acpi_add_table(table_offsets, tables_blob);
>      build_spcr(tables_blob, tables->linker, vms);
>  
> +    acpi_add_table(table_offsets, tables_blob);
> +    build_dbg2(tables_blob, tables->linker, vms);
> +
>      if (vms->ras) {
>          build_ghes_error_table(tables->hardware_errors, tables->linker);
>          acpi_add_table(table_offsets, tables_blob);
> -- 
> 2.26.3
>

Thanks,
drew