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

["Pete Batard" <pete@akeo.ie>]

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
>> +  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.

Regards,

/Pete

>> +  // 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);
>>   }
>>
>