• Timur Tabi's avatar
    powerpc/85xx: use the BRx registers to enable indirect mode on the P1022DS · 6bd825f0
    Timur Tabi authored
    In order to enable the DIU video controller on the P1022DS, the FPGA needs
    to be switched to "indirect mode", where the localbus is disabled and
    the FPGA is accessed via writes to localbus chip select signals CS0 and CS1.
    
    To obtain the address of CS0 and CS1, the platform driver uses an "indirect
    pixis mode" device tree node.  This node assumes that the localbus 'ranges'
    property is sorted in chip-select order.  That is, reg value 0 maps to
    CS0, reg value 1 maps to CS1, etc.  This is how the 'ranges' property is
    supposed to be arranged.
    
    Unfortunately, the 'ranges' property is often mis-arranged, and not just on
    the P1022DS.  Linux normally does not care, since it does not program the
    localbus.  But the indirect-mode code on the P1022DS does care.
    
    The "proper" fix is to have U-Boot fix the 'ranges' property, but this would
    be too cumbersome.  The names and 'reg' properties of all the localbus
    devices would also need to be updated, and determining which localbus device
    maps to which chip select is board-specific.
    
    Instead, we determine the CS0/CS1 base addresses the same way that U-boot
    does -- by reading the BRx registers directly and mapping them to physical
    addresses.  This code is simpler and more reliable, and it does not require
    a U-boot or device tree change.
    
    Since the indirect pixis device tree node is no longer needed, the node is
    deleted from the DTS.
    Signed-off-by: default avatarTimur Tabi <timur@freescale.com>
    Signed-off-by: default avatarKumar Gala <galak@kernel.crashing.org>
    6bd825f0
p1022_ds.c 14.5 KB