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>
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@ -595,6 +595,7 @@ static int ar_context_add_page(struct ar_context *ctx)
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ab->descriptor.res_count = cpu_to_le16(PAGE_SIZE - offset);
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ab->descriptor.res_count = cpu_to_le16(PAGE_SIZE - offset);
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ab->descriptor.branch_address = 0;
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ab->descriptor.branch_address = 0;
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wmb(); /* finish init of new descriptors before branch_address update */
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ctx->last_buffer->descriptor.branch_address = cpu_to_le32(ab_bus | 1);
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ctx->last_buffer->descriptor.branch_address = cpu_to_le32(ab_bus | 1);
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ctx->last_buffer->next = ab;
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ctx->last_buffer->next = ab;
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ctx->last_buffer = ab;
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ctx->last_buffer = ab;
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@ -982,6 +983,8 @@ static void context_append(struct context *ctx,
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d_bus = desc->buffer_bus + (d - desc->buffer) * sizeof(*d);
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d_bus = desc->buffer_bus + (d - desc->buffer) * sizeof(*d);
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desc->used += (z + extra) * sizeof(*d);
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desc->used += (z + extra) * sizeof(*d);
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wmb(); /* finish init of new descriptors before branch_address update */
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ctx->prev->branch_address = cpu_to_le32(d_bus | z);
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ctx->prev->branch_address = cpu_to_le32(d_bus | z);
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ctx->prev = find_branch_descriptor(d, z);
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ctx->prev = find_branch_descriptor(d, z);
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