[ARM] pxafb: allow video memory size to be configurable

The amount of video memory size is decided according to the following
order:

1. <xres> x <yres> x <bits_per_pixel> by default, which is the backward
   compatible way

2. size specified in platform data

3. size specified in module parameter 'options' string or specified in
   kernel boot command line (see updated Documentation/fb/pxafb.txt)

And now since the memory is allocated from system memory, the pxafb_mmap
can be removed and the default fb_mmap() should be working all right.

Also, since we now have introduced the 'struct pxafb_dma_buff' for DMA
descriptors and palettes, the allocation can be separated cleanly.

NOTE: the LCD DMA actually supports chained transfer (i.e. page-based
transfers), to simplify the logic and keep the performance (with less
TLB misses when accessing from memory mapped user space), the memory
is allocated by alloc_pages_*() to ensures it's physical contiguous.

Signed-off-by: Eric Miao <eric.miao@marvell.com>
Signed-off-by: Eric Miao <ycmiao@ycmiao-hp520.(none)>

1 files changed, 6 insertions, 2 deletions

diff --git a/Documentation/fb/pxafb.txt b/Documentation/fb/pxafb.txt
index db9b850..ad94b5c 100644
--- a/Documentation/fb/pxafb.txt
+++ b/Documentation/fb/pxafb.txt
@@ -5,9 +5,13 @@ The driver supports the following options, either via
 options=<OPTIONS> when modular or video=pxafb:<OPTIONS> when built in.
 
 For example:
-	modprobe pxafb options=mode:640x480-8,passive
+	modprobe pxafb options=vmem:2M,mode:640x480-8,passive
 or on the kernel command line
-	video=pxafb:mode:640x480-8,passive
+	video=pxafb:vmem:2M,mode:640x480-8,passive
+
+vmem: VIDEO_MEM_SIZE
+	Amount of video memory to allocate (can be suffixed with K or M
+	for kilobytes or megabytes)
 
 mode:XRESxYRES[-BPP]
 	XRES == LCCR1_PPL + 1