Re: [edk2-devel] [edk2-platforms][PATCH v3 5/5] Platform/RPi3/PlatformSmbiosDxe: Derive RAM size from board revision

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 10/14/19 2:03 PM, Pete Batard wrote:
> On 2019.10.14 12:53, Philippe Mathieu-Daudé wrote:
>> On 10/14/19 1:44 PM, Pete Batard wrote:
>>> Hi Philippe,
>>>
>>> On 2019.10.14 11:01, Philippe Mathieu-Daudé wrote:
>>>> Hi Pete,
>>>>
>>>> On 10/11/19 1:07 PM, Pete Batard wrote:
>>>>> The board revision is the proper channel to use to detect the 
>>>>> amount of
>>>>> RAM available as bits [20-22] report the effective RAM size for the 
>>>>> board
>>>>> starting with 256 MB (000b) and doubling in size for each value.
>>>>>
>>>>> Signed-off-by: Pete Batard <pete@akeo.ie>
>>>>> Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
>>>>> ---
>>>>> Platform/RaspberryPi/RPi3/Drivers/PlatformSmbiosDxe/PlatformSmbiosDxe.c 
>>>>> | 18 ++++++++++++------
>>>>>   1 file changed, 12 insertions(+), 6 deletions(-)
>>>>>
>>>>> diff --git 
>>>>> a/Platform/RaspberryPi/RPi3/Drivers/PlatformSmbiosDxe/PlatformSmbiosDxe.c 
>>>>> b/Platform/RaspberryPi/RPi3/Drivers/PlatformSmbiosDxe/PlatformSmbiosDxe.c 
>>>>>
>>>>> index b5dcff897a59..5abc82b8d363 100644
>>>>> --- 
>>>>> a/Platform/RaspberryPi/RPi3/Drivers/PlatformSmbiosDxe/PlatformSmbiosDxe.c 
>>>>>
>>>>> +++ 
>>>>> b/Platform/RaspberryPi/RPi3/Drivers/PlatformSmbiosDxe/PlatformSmbiosDxe.c 
>>>>>
>>>>> @@ -866,16 +866,22 @@ MemArrMapInfoUpdateSmbiosType19 (
>>>>>     )
>>>>>   {
>>>>>     EFI_STATUS Status;
>>>>> -  UINT32 Base;
>>>>> -  UINT32 Size;
>>>>> +  UINT32 BoardRevision = 0;
>>>>> -  Status = mFwProtocol->GetArmMem (&Base, &Size);
>>>>> +  // Note: Type 19 addresses are expressed in KB, not bytes
> 
> Comment to add:
> 
> // The memory layout used in all known Pi SoC's starts at 0

Thanks, Leif do you mind amending this comment?

Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>

>>>>> +  mMemArrMapInfoType19.StartingAddress = 0;
>>>>
>>>> Now you assume the ARM base RAM address is always 0, why?
>>>
>>> Because, in the case that is of interest to us here (Broadcom SoCs 
>>> used for the various Raspberry Pi platforms), this is what the 
>>> documentation says.
>>>
>>> If you look at something like 
>>> https://www.raspberrypi.org/app/uploads/2012/02/BCM2835-ARM-Peripherals.pdf 
>>> (which, as per the Pi Foundation, also applies to the later models) 
>>> and especially the memory layout graphic that you see early in the 
>>> document, you can find that the ARM base RAM address is indeed set to 
>>> 0 always.
>>>
>>> At this stage, we have no reason to think that we are going to 
>>> contend with a model where the RAM base address isn't 0.
>>
>> OK. I have no idea what are Broadcom plans, I read somewhere they were 
>> going to use tricks to allow more than 4GB of RAM on the Raspberry Pi 
>> 4, so I was wondering, since they provide a firmware API call to get 
>> the RAM base address.
> 
> Well the thing is, this patch comes straight from work that is being 
> carried out to add support for the Pi 4 to edk2-platforms. So we pretty 
> much already validated that 0 is what needs to be used for the Pi 4 as 
> well...

OK, good news :)

>> Maybe you can add a comment that we expect all following boards to use 
>> RAM base at 0 (simply replying to this email, and eventually Leif 
>> would amend it previous to push).
> 
> Sure. Comment added above.

Thanks!

> Regards,
> 
> /Pete
> 
>>
>> Otherwise your patch looks OK.
>>
>> Regards,
>>
>> Phil.
>>
>>>>> +  // The minimum RAM size used on any Raspberry Pi model is 256 MB
>>>>> +  mMemArrMapInfoType19.EndingAddress = 256 * 1024;
>>>>> +  Status = mFwProtocol->GetModelRevision (&BoardRevision);
>>>>>     if (Status != EFI_SUCCESS) {
>>>>> -    DEBUG ((DEBUG_ERROR, "Couldn't get the ARM memory size: %r\n", 
>>>>> Status));
>>>>> +    DEBUG ((DEBUG_WARNING, "Couldn't get the board memory size - 
>>>>> defaulting to 256 MB: %r\n", Status));
>>>>>     } else {
>>>>> -    mMemArrMapInfoType19.StartingAddress = Base / 1024;
>>>>> -    mMemArrMapInfoType19.EndingAddress = (Base + Size - 1) / 1024;
>>>>> +    // 
>>>>> www.raspberrypi.org/documentation/hardware/raspberrypi/revision-codes/README.md 
>>>>>
>>>>> +    // Bits [20-22] indicate the amount of memory starting with 
>>>>> 256MB (000b)
>>>>> +    // and doubling in size for each value (001b = 512 MB, 010b = 
>>>>> 1GB, etc.)
>>>>> +    mMemArrMapInfoType19.EndingAddress <<= (BoardRevision >> 20) & 
>>>>> 0x07;
>>>>>     }
>>>>> +  mMemArrMapInfoType19.EndingAddress -= 1;
>>>>>     LogSmbiosData ((EFI_SMBIOS_TABLE_HEADER*)&mMemArrMapInfoType19, 
>>>>> mMemArrMapInfoType19Strings, NULL);
>>>>>   }
>>>>>
>>>>
>>>
>>>
>>> 
>>>
>>
>