• Maxime Coquelin's avatar
    ARM: dts: stm32f429: Boost perfs by remapping SDRAM Bank 1 to 0x0 · b2aa7f77
    Maxime Coquelin authored
    STM32F429 allows to remap FMC SDRAM Bank 1 from 0xc0000000 to 0x0,
    by writing 0x4 to SYSCFG_MEMRMP register.
    
    As mentionned in the reference manual (see chapter 9.3.1), the performance
    gain is really interresting:
    "In remap mode at address 0x0000 0000, the CPU can access the external
    memory via ICode bus instead of System bus which boosts up the
    performance."
    
    These are the dhrystone results with and without the remap enabled:
    Default (SDRAM in 0xc0000000):
    ---------------------------------
    Microseconds for one run through Dhrystone:   31.8
    Dhrystones per Second:                      31416.9
    
    Remap (SDRAM in 0x0000000):
    -----------------------------
    Microseconds for one run through Dhrystone:   20.6
    Dhrystones per Second:                      48520.1
    
    This patch first change the SDRAM start address to 0x0 for STM32429i-EVAL
    board, and also set the dma-range property as the other masters than the M4
    CPU still see SDRAM in 0xc0000000.
    
    Note that the Discovery board cannot benefit from this feature, since the
    SDRAM is connected to Bank 2.
    Signed-off-by: default avatarMaxime Coquelin <mcoquelin.stm32@gmail.com>
    b2aa7f77
stm32429i-eval.dts 2.87 KB