[PATCH] firewire: fw-ohci: sync AT dma buffer before use

[Jarod Wilson <jwilson@redhat.com>]

Per DMA API docs, when using dma_map_single(), DMA_TO_DEVICE synchronization
must be done after the last modification of the memory region by software
before it can be handed off to the device and safely read. Such a sync is
currently missing from firewire_ohci:at_context_queue_packet().

At least on my setup, where I could within seconds reliably reproduce a panic
in handle_at_packet() by simply dd'ing from two drives on different controllers,
the panic is gone.

See http://bugzilla.kernel.org/show_bug.cgi?id=9617

Signed-off-by: Jarod Wilson <jwilson@redhat.com>

---

 drivers/firewire/fw-ohci.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/firewire/fw-ohci.c b/drivers/firewire/fw-ohci.c
index 081a434..fc45868 100644
--- a/drivers/firewire/fw-ohci.c
+++ b/drivers/firewire/fw-ohci.c
@@ -780,6 +780,10 @@ at_context_queue_packet(struct context *ctx, struct fw_packet *packet)
 
 	context_append(ctx, d, z, 4 - z);
 
+	/* Sync the DMA buffer up for the device to read from */
+	dma_sync_single_for_device(ohci->card.device, payload_bus,
+				   packet->payload_length, DMA_TO_DEVICE);
+
 	/* If the context isn't already running, start it up. */
 	reg = reg_read(ctx->ohci, CONTROL_SET(ctx->regs));
 	if ((reg & CONTEXT_RUN) == 0)

-- 
Jarod Wilson
jwilson@redhat.com