• Noralf Trønnes's avatar
    fbdev: fb_defio: Export fb_deferred_io_mmap · ba026334
    Noralf Trønnes authored
    Export fb_deferred_io_mmap so drivers can change vma->vm_page_prot.
    When the framebuffer memory is allocated using dma_alloc_writecombine()
    instead of vmalloc(), I get cache syncing problems on ARM.
    This solves it:
    
    static int drm_fbdev_cma_deferred_io_mmap(struct fb_info *info,
    					  struct vm_area_struct *vma)
    {
    	fb_deferred_io_mmap(info, vma);
    	vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
    
    	return 0;
    }
    
    Could this have been done in the core?
    Drivers that don't set (struct fb_ops *)->fb_mmap, gets a call to
    fb_pgprotect() at the end of the default fb_mmap implementation
    (drivers/video/fbdev/core/fbmem.c). This is an architecture specific
    function that on many platforms uses pgprot_writecombine(), but not on
    all. And looking at some of the fb_mmap implementations, some of them
    sets vm_page_prot to nocache for instance, so I think the safest bet is
    to do this in the driver and not in the fbdev core. And we can't call
    fb_pgprotect() from fb_deferred_io_mmap() either because we don't have
    access to the file pointer that powerpc needs.
    Signed-off-by: 's avatarNoralf Trønnes <noralf@tronnes.org>
    Acked-by: 's avatarTomi Valkeinen <tomi.valkeinen@ti.com>
    Signed-off-by: 's avatarDaniel Vetter <daniel.vetter@ffwll.ch>
    Link: http://patchwork.freedesktop.org/patch/msgid/1461856717-6476-5-git-send-email-noralf@tronnes.org
    ba026334
fb.h 29 KB