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firewire: ohci: use memory barriers to order descriptor updates 

When we append to a DMA program, we need to ensure that the order in
which initialization of the new descriptors and update of the
branch_address of the old tail descriptor, as seen by the PCI device,
happen as intended.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
This commit is contained in:
Stefan Richter 2010-07-27 13:20:33 +02:00
parent 8e2b2b46ea
commit 071595ebdc
1 changed files with 3 additions and 0 deletions
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3
drivers/firewire/ohci.c
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@ -595,6 +595,7 @@ static int ar_context_add_page(struct ar_context *ctx)
ab->descriptor.res_count = cpu_to_le16(PAGE_SIZE - offset);
ab->descriptor.branch_address = 0;
wmb(); /* finish init of new descriptors before branch_address update */
ctx->last_buffer->descriptor.branch_address = cpu_to_le32(ab_bus | 1);
ctx->last_buffer->next = ab;
ctx->last_buffer = ab;
@ -982,6 +983,8 @@ static void context_append(struct context *ctx,
d_bus = desc->buffer_bus + (d - desc->buffer) * sizeof(*d);
desc->used += (z + extra) * sizeof(*d);
wmb(); /* finish init of new descriptors before branch_address update */
ctx->prev->branch_address = cpu_to_le32(d_bus | z);
ctx->prev = find_branch_descriptor(d, z);