[ts-7000] strange problem mmap

["chaisc97" <>]

i try to write a video driver for ts7200 using s1d13506. now the lcd
has start, now the problem is i can write the data to the video
memeory however when i read the data i get the wrong value, what's
wrong with my code?

the **_mmap like this
s1d13xxx_mmap(struct fb_info *info, struct file *file, struct
vm_area_struct *vma)
{

       unsigned long off, start;
        u32 len;
        unsigned long size  = vma->vm_end - vma->vm_start;
        off = vma->vm_pgoff << PAGE_SHIFT;
        start = S1D_PHYSICAL_VMEM_ADDR;
        unsigned long page, pos;

        len = PAGE_ALIGN(start & ~PAGE_MASK) + S1D_PHYSICAL_VMEM_SIZE;
/*
S1D_PHYSICAL_VMEM_ADDR=0x20000000
S1D_PHYSICAL_VMEM_SIZE=0x200000L
*/

        start &= PAGE_MASK;

        if ((vma->vm_end - vma->vm_start + off) > len)
                return -EINVAL;

        off += start;

        vma->vm_pgoff = off >> PAGE_SHIFT;

        vma->vm_flags |= VM_IO;

        start=vma->vm_start;
        size=vma->vm_end - vma->vm_start;
        pos=off;//S1D_PHYSICAL_VMEM_ADDR;
        while(size>0)
while(size>0)
        {
                 if (io_remap_page_range(start,pos,PAGE_SIZE,
PAGE_SHARED))
                        return -EAGAIN;
                        start += PAGE_SIZE;
                         pos += PAGE_SIZE;
                 if (size > PAGE_SIZE)
                        size -= PAGE_SIZE;
                else
                        size = 0;
        }



 
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