• Brian Norris's avatar
    mtd: m25p80: remove M25PXX_USE_FAST_READ Kconfig · ddba7c5a
    Brian Norris authored
    Remove the compile-time option for FAST_READ, since we have run-time
    support for detecting it. This refactors the logic for enabling
    fast-read, such that for DT-enabled devices, we honor the
    "m25p,fast-read" property but for non-DT devices, we default to using
    FAST_READ whenever the flash device supports it.
    
    Normal READ and FAST_READ differ only in the following:
    
      * FAST_READ supports SPI higher clock frequencies [1]
    
      * number of dummy cycles; FAST_READ requires 8 dummy cycles (whereas
        READ requires 0) to allow the flash sufficient setup time, even when
        running at higher clock speeds
    
    Thus, for flash chips which support FAST_READ, there is otherwise no
    limiting reason why we cannot use the FAST_READ opcode instead of READ.
    It simply allows the SPI controller to run at higher clock rates. So
    theoretically, nobody should be needing the compile-time option anyway.
    
      [1] I have a Spansion S25FL128S datasheet which says:
    
        "The maximum operating clock frequency for the READ command is 50
        MHz."
    
      And:
    
        "The maximum operating clock frequency for FAST READ command is 133
        MHz."
    Signed-off-by: default avatarBrian Norris <computersforpeace@gmail.com>
    ddba7c5a
Kconfig 7.74 KB