[PATCH] firewire: Enable remote DMA above 4 GB

From: Stefan Richter
Date: Sat Jan 18 2014 - 10:33:37 EST


This makes all of a machine's memory accessible to remote debugging via
FireWire, using the physical response unit (i.e. RDMA) of OHCI-1394 link
layer controllers.

This requires actual support by the controller. The only ones currently
known to support it are Agere/LSI FW643. Most if not all other OHCI-1394
controllers do not implement the optional Physical Upper Bound register.
With them, RDMA will continue to be limited to the lowermost 4 GB.

firewire-ohci's startup message in the kernel log is augmented to tell
whether the controller does expose more than 4 GB to RDMA.

While OHCI-1394 allows for a maximum Physical Upper Bound of
0xffff'0000'0000 (near 256 TB), this implementation sets it to
0x8000'0000'0000 (128 TB) in order to avoid interference with applications
that require interrupt-served asynchronous request reception at
respectively low addresses.

Derived from patch "firewire: Enable physical DMA above 4GB" by
Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> from March 27, 2013.

Signed-off-by: Stefan Richter <stefanr@xxxxxxxxxxxxxxxxx>
---
drivers/firewire/core-transaction.c | 6 +++---
drivers/firewire/core.h | 3 +++
drivers/firewire/ohci.c | 8 +++++---
3 files changed, 11 insertions(+), 6 deletions(-)

--- a/drivers/firewire/core-transaction.c
+++ b/drivers/firewire/core-transaction.c
@@ -523,11 +523,11 @@ static DEFINE_SPINLOCK(address_handler_l
static LIST_HEAD(address_handler_list);

const struct fw_address_region fw_high_memory_region =
- { .start = 0x000100000000ULL, .end = 0xffffe0000000ULL, };
+ { .start = FW_MAX_PHYSICAL_RANGE, .end = 0xffffe0000000ULL, };
EXPORT_SYMBOL(fw_high_memory_region);

static const struct fw_address_region low_memory_region =
- { .start = 0x000000000000ULL, .end = 0x000100000000ULL, };
+ { .start = 0x000000000000ULL, .end = FW_MAX_PHYSICAL_RANGE, };

#if 0
const struct fw_address_region fw_private_region =
@@ -1217,7 +1217,7 @@ static void handle_low_memory(struct fw_
}

static struct fw_address_handler low_memory = {
- .length = 0x000100000000ULL,
+ .length = FW_MAX_PHYSICAL_RANGE,
.address_callback = handle_low_memory,
};

--- a/drivers/firewire/core.h
+++ b/drivers/firewire/core.h
@@ -237,6 +237,9 @@ static inline bool is_next_generation(in

#define LOCAL_BUS 0xffc0

+/* arbitrarily chosen maximum range for physical DMA: 128 TB */
+#define FW_MAX_PHYSICAL_RANGE (128ULL << 40)
+
void fw_core_handle_request(struct fw_card *card, struct fw_packet *request);
void fw_core_handle_response(struct fw_card *card, struct fw_packet *packet);
int fw_get_response_length(struct fw_request *request);
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -2367,7 +2367,7 @@ static int ohci_enable(struct fw_card *c
reg_write(ohci, OHCI1394_FairnessControl, 0);
card->priority_budget_implemented = ohci->pri_req_max != 0;

- reg_write(ohci, OHCI1394_PhyUpperBound, 0x00010000);
+ reg_write(ohci, OHCI1394_PhyUpperBound, FW_MAX_PHYSICAL_RANGE >> 16);
reg_write(ohci, OHCI1394_IntEventClear, ~0);
reg_write(ohci, OHCI1394_IntMaskClear, ~0);

@@ -3723,9 +3723,11 @@ static int pci_probe(struct pci_dev *dev
version = reg_read(ohci, OHCI1394_Version) & 0x00ff00ff;
ohci_notice(ohci,
"added OHCI v%x.%x device as card %d, "
- "%d IR + %d IT contexts, quirks 0x%x\n",
+ "%d IR + %d IT contexts, quirks 0x%x%s\n",
version >> 16, version & 0xff, ohci->card.index,
- ohci->n_ir, ohci->n_it, ohci->quirks);
+ ohci->n_ir, ohci->n_it, ohci->quirks,
+ reg_read(ohci, OHCI1394_PhyUpperBound) ?
+ ", >4 GB phys DMA" : "");

return 0;



--
Stefan Richter
-=====-====- ---= =--=-
http://arcgraph.de/sr/
--
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