Re: [edk2-devel] Additional configuration options on Armada/Cn913x

["Ard Biesheuvel" <ard.biesheuvel@arm.com>]

On 6/12/20 12:43 AM, Mark Kettenis via Groups.Io wrote:
> On Thu, Jun 11, 2020 at 04:17 PM, Ard Biesheuvel wrote:
> 
>     On 6/11/20 4:07 PM, greg@unrelenting.technology wrote:
> 
>         June 11, 2020 4:19 PM, "Ard Biesheuvel" <ard.biesheuvel@arm.com>
>         wrote:
> 
>             On 6/5/20 5:19 PM, Marcin Wojtas via groups.io wrote:
> 
>                 Hi,
>                 I'd like to ask for comments before I develop the actual
>                 code - > currently we have 2 workarounds
>                 done specifically for Linux:
>                 a. ECAM shift in PCIE
>                 b. SPCR address space definition
> 
>             What does this mean?
> 
>         The SPCR in upstream edk2 is set up to work around some Linux
>         weirdness (?) and I have to do this:
> 
>         https://github.com/myfreeweb/edk2-platforms/commit/74ec98a6498e78d2ae6c861db88487bf75f2e1a1
> 
>         to make it work on FreeBSD.
> 
>     Surely, they can't both be correct. Marcin?
> 
> Assuming the serial port on Armada/Cn911x is the same as on Armada8k, 
> the following DT properties would be applicable:
> 
> reg-shift = <2>;
> reg-io-width = <1>
> 
> which means the registers are spaced 32-bits apart but have to be 
> accessed using 8-bit load/store instructions.  I'd say that
> means that the ACPI Generic Address Space should have RegisterBitWidth 
> set to 32 and AccessSize set to BYTE.
> In other words, I think that the current:
> 
> #define MV_UART_AS32(Address) { EFI_ACPI_5_0_SYSTEM_MEMORY, 32, 0, 
> EFI_ACPI_5_0_BYTE, Address }
> 
> is correct.  That certainly is what works for OpenBSD.

Thanks Mark

The struct type is defined as

typedef struct {
   UINT8   AddressSpaceId;
   UINT8   RegisterBitWidth;
   UINT8   RegisterBitOffset;
   UINT8   AccessSize;
   UINT64  Address;
} EFI_ACPI_5_0_GENERIC_ADDRESS_STRUCTURE;

so I agree that the current definition matches a UART that requires byte 
accesses on registers that are 32 bits apart.

So why does FreeBSD deviate from this?