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

[Igor Mammedov]

On Wed, 6 Oct 2021 11:57:07 +0200
Eric Auger <eric.auger@redhat.com> wrote:

> 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 /
> 

"Table 1. Debug Port Table 2 format"
says table revision must be 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.

indeed '+' before comment should look better

> >  
> >> +                       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 
> >  
>