Re: [PATCH V4 2/3] powerpc/swiotlb: Enable at early stage and disable if not necessary

On Fri, Aug 3, 2012 at 8:38 PM, Kumar Gala [off-list ref] wrote:

On Aug 2, 2012, at 9:21 PM, Jia Hongtao-B38951 wrote:

quoted

quoted

-----Original Message-----
From: Kumar Gala [mailto:galak@kernel.crashing.org]
Sent: Thursday, August 02, 2012 8:55 PM
To: Jia Hongtao-B38951
Cc: linuxppc-dev@lists.ozlabs.org; Wood Scott-B07421; Li Yang-R58472
Subject: Re: [PATCH V4 2/3] powerpc/swiotlb: Enable at early stage and
disable if not necessary


On Aug 2, 2012, at 6:42 AM, Jia Hongtao wrote:

quoted

Remove the dependency on PCI initialization for SWIOTLB initialization.
So that PCI can be initialized at proper time.

SWIOTLB is partly determined by PCI inbound/outbound map which is

assigned

quoted

in PCI initialization. But swiotlb_init() should be done at the stage

of

quoted

mem_init() which is much earlier than PCI initialization. So we reserve

the

quoted

memory for SWIOTLB first and free it if not necessary.

All boards are converted to fit this change.

Signed-off-by: Jia Hongtao <redacted>
Signed-off-by: Li Yang <redacted>
---

This doesn't seem like it addresses our issue w/regards to not being able
to map all of memory from PCI.

PCI init will determine ppc_swiotlb_enable due to PCI map. swiotlb_late_init
will handle all swiotlb things depend on the result of pci init.

Think about the case that we have 4095M of memory & 1G of PCI memory mapped space.  The old code would enable swiotlb for this case since we would NOT be able to DMA to all 4095M of memory.  The patch does not handle this case correctly.

The patch can handle it.  The ppc_swiotlb_enable is still being set in
 fsl_pci_init() if there is 1G of PCI memory mapped space.  It is
after next patch that the ppc_swiotlb_enable is being set in the PCI
probe() routine.

Leo