• Matt Fleming's avatar
    efifb: Add support for 64-bit frame buffer addresses · ae2ee627
    Matt Fleming authored
    The EFI Graphics Output Protocol uses 64-bit frame buffer addresses
    but these get truncated to 32-bit by the EFI boot stub when storing
    the address in the 'lfb_base' field of 'struct screen_info'.
    
    Add a 'ext_lfb_base' field for the upper 32-bits of the frame buffer
    address and set VIDEO_TYPE_CAPABILITY_64BIT_BASE when the field is
    useable.
    
    It turns out that the reason no one has required this support so far
    is that there's actually code in tianocore to "downgrade" PCI
    resources that have option ROMs and 64-bit BARS from 64-bit to 32-bit
    to cope with legacy option ROMs that can't handle 64-bit addresses.
    The upshot is that basically all GOP devices in the wild use a 32-bit
    frame buffer address.
    
    Still, it is possible to build firmware that uses a full 64-bit GOP
    frame buffer address. Chad did, which led to him reporting this issue.
    
    Add support in anticipation of GOP devices using 64-bit addresses more
    widely, and so that efifb works out of the box when that happens.
    Reported-by: default avatarChad Page <chad.page@znyx.com>
    Cc: Pete Hawkins <pete.hawkins@znyx.com>
    Acked-by: default avatarPeter Jones <pjones@redhat.com>
    Cc: Matthew Garrett <mjg59@srcf.ucam.org>
    Cc: Geert Uytterhoeven <geert@linux-m68k.org>
    Signed-off-by: default avatarMatt Fleming <matt.fleming@intel.com>
    ae2ee627
efifb.c 9.5 KB