Date: Tue, 27 Jul 2010 13:20:33 +0200 (CEST) From: Stefan Richter Subject: 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 --- drivers/firewire/ohci.c | 3 +++ 1 file changed, 3 insertions(+) Index: b/drivers/firewire/ohci.c =================================================================== --- a/drivers/firewire/ohci.c +++ b/drivers/firewire/ohci.c @@ -595,6 +595,7 @@ static int ar_context_add_page(struct ar 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 contex 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);