Re: [Qemu-arm] [PATCH v2 04/11] hw/arm/aspeed: add a 'execute-in-place' property to boot directly from CE0

[Cédric Le Goater]

On 10/2/18 12:49 PM, Peter Maydell wrote:
> On 21 September 2018 at 17:19, Cédric Le Goater <address@hidden> wrote:
>> The overhead for the OpenBMC firmware images using the a custom U-Boot
>> is around 2 seconds, which is fine, but with a U-Boot from mainline,
>> it takes an extra 50 seconds or so to reach Linux. A quick survey on
>> the number of reads performed on the flash memory region gives the
>> following figures :
>>
>>   OpenBMC U-Boot      922478 (~ 3.5 MBytes)
>>   Mainline U-Boot   20569977 (~ 80  MBytes)
>>
>> QEMU must be trashing the TCG TBs and reloading text very often. Some
>> addresses are read more than 250.000 times. Until we find a solution
>> to improve boot time, execution from MMIO is not activated by default.
>>
>> Setting this option also breaks migration compatibility.
>>
>> Signed-off-by: Cédric Le Goater <address@hidden>
> 
> Reviewed-by: Peter Maydell <address@hidden>


The DRAM training in mainline u-boot is also significantly slower on 
real HW. I haven't spotted the exact area but the code is jumping back
and forth.  This patch should help tracking the culprit.
   
Thanks,

C.