Messages in this thread | | | Date | Tue, 1 Feb 2011 16:18:59 -0500 | From | Chuck Ebbert <> | Subject | Re: b44 driver causes panic when using swiotlb |
| |
On Tue, 1 Feb 2011 10:28:00 +0900 FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
> > swiotlb allocates the bounce buffer when a system boots up. We can't > allocate much in GFP_DMA. swiotlb uses somewhere under 4GB. So it > can't help devices that have odd dma_mask (that is, except for 4GB). > > Unfortunately, Such device needs to do own custom bouncing or needs > their subsystem to does that.
I think we're chasing the wrong problem here.
swiotlb uses alloc_bootmem_low_pages() to try to get buffers as low in memory as possible. I asked someone who is hitting this bug to try 2.6.36 and he reports the buffers really are low there:
2.6.36: 5c00000 2.6.37: db600000
So something happened very early in the 2.6.37-rc cycle that changed this behavior. I tried looking at the bootmem code but could not see the problem. The only related option I could find in .config was this:
# CONFIG_NO_BOOTMEM is not set
It was set this way in both .36 and .37.
| |