Messages in this thread |  | | | Subject | Re: [PATCH] firewire: fw-ohci: sync AT dma buffer before use | | From | David Moore <> | | Date | Wed, 12 Mar 2008 18:35:49 -0400 |
| |
On Wed, 2008-03-12 at 17:43 -0400, Jarod Wilson wrote: > 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) >
Two things:
1. The dma_sync should probably be done before the context_append because the controller could in theory start reading the data as soon as context_append is called right?
2. As an optimization, we should attempt to allocate the payload in the lower 32-bits of physical memory, to prevent extra memcopies on x86_64. I think this can be done by adding GFP_DMA32 to kmalloc where the payload was allocated in fw-cdev.c. There might be other places where we would benefit from GFP_DMA32 also. Of course, these optimizations are probably better saved for another patch.
-David
|  |