Re: [PATCH] powerpc/iommu/ddw: Fix endianness

On Mon, 2014-09-15 at 18:41 +1000, Alexey Kardashevskiy wrote:

On 09/09/2014 09:22 PM, Alexey Kardashevskiy wrote:

quoted

rtas_call() accepts and returns values in CPU endianness.

Sounds right.

quoted

of_read_number() accepts big-endian values but create.addr_hi/lo returned
by rtas_call() are in CPU endiannes.

Also sounds right.

quoted

The dynamic_dma_window_prop struct defines all members as BE so let's
make it true.

It does. But why does it do that? It seems to be allocated and setup in
enable_ddw() and then the only place I see it used is in
tce_setrange_multi_pSeriesLP()/tce_clearrange_multi_pSeriesLP(), which both
unpack it again. What am I missing?

quoted

struct dynamic_dma_window_prop {
        __be32  liobn;          /* tce table number */
        __be64  dma_base;       /* address hi,lo */
        __be32  tce_shift;      /* ilog2(tce_page_size) */
        __be32  window_shift;   /* ilog2(tce_window_size) */
};

We do read them from the device tree in find_existing_ddw_windows(), but if
that's the only place then the conversion to cpu endian should happen there.

quoted

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 7c1d77c..700020a 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c

@@ -750,7 +750,7 @@ static void remove_ddw(struct device_node *np, bool remove_prop)
 		pr_debug("%s successfully cleared tces in window.\n",
 			 np->full_name);
 
-	ret = rtas_call(ddw_avail[2], 1, 1, NULL, liobn);
+	ret = rtas_call(be32_to_cpu(ddw_avail[2]), 1, 1, NULL, liobn);

The conversion should happen once where ever ddw_avail comes out of the device
tree, rather than everywhere it's used.

cheers