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

[Eric Auger]

Hi,

On 10/6/21 11:15 AM, Andrew Jones wrote:
> 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."
The above revision field belongs to the acpi table header. Not to be
mixed with the Revision field of the DBG2 table
which is set below (set to 0):

+    build_append_int_noprefix(table_data, 0, 1); /* Revision */

Besides that's a good question. I have rev=3 here but that must come from a 
copy/paste. when googling I
found

https://lists.denx.de/pipermail/u-boot/2015-June/217134.html
/header->revision = 1; /* ACPI 1.0/2.0: 1, ACPI 3.0: 2, ACPI 4.0: 3 */
Not sure if 3 is the right value though? Igor, please could you advise?
Thanks Eric /

>
>
>> +                        .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 
>