Thread (4 messages) 4 messages, 2 authors, 2011-05-03

dma_alloc_writecombine() and MAX_ORDER

From: Russell King - ARM Linux <hidden>
Date: 2011-05-03 08:44:37

On Tue, May 03, 2011 at 08:25:32AM +0200, Michael Hunold wrote:
Hello Russell,

on 04/29/2011 04:27 PM Russell King - ARM Linux said the following:
quoted
On Fri, Apr 29, 2011 at 02:50:37PM +0200, Michael Hunold wrote:
quoted
quoted
Now I have a new panel with a higher resolution and more bits-per-pixel.
I want to use double-buffering with DirectFB and so my framebuffer size
exceeds 4Mb.
quoted
You could try this patch.  It steals the memory for the coherent and
writecombine memory at boot time, so MAX_ORDER no longer comes into the
problem.  You may need to define CONSISTENT_WC_SIZE and CONSISTENT_DMA_SIZE
appropriately to gain sufficient memory.  Note that the sum of those two
must be a multiple of 2MB, and individually must be a multiple of 1MB.
I really want to try this patch out, but unfortunately, I don't know to
which tree I can apply it to. :-(
You may need 516295e (ARM: pgtable: add pud-level code) from a later
kernel as well then.
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