In the SG case this is already handled since a non-zero
request->num_mapped_sgs is a clear indicator that dma_map_sg()
had been called. While it would be nice to do the same for the
singly mapped case by simply checking for non-zero request->dma,
it's conceivable that 0 is a valid dma_addr_t handle. Hence add
a flag 'dma_mapped' to struct usb_request and use this to
determine the need to call dma_unmap_single(). Otherwise, if a
request is not DMA mapped then the result of calling
usb_request_unmap_request() would safely be a no-op.
Signed-off-by: Jack Pham <ja...@codeaurora.org>
---
Hi Felipe,
Here's what I came up with after our discussion back in [1]. It
turned out to be pretty dead-simple and hopefully doesn't need to
approach the number of URB flags that the host core uses.
I did a quick survey of all callers of usb_gadget_{map,unmap}_request
and besides the instance I reported & patched in dwc3, from what I
can tell it looks like all the other gadget drivers seem to be calling
these APIs sanely--i.e. a request is only queued after being
successfully mapped, and unmap only ever gets called on requests that
had been queued.
Although in one instance (renesas_usb3.c), there is a 'used' flag as
part of struct renesas_usb3_dma that looks like it's tracking the
status of whether a request is mapped or not, but it's not obvious from
cursory glance whether it has a use besides that or if it would be
sufficient to just rely on this new flag in struct usb_gadget.
Maybe Yoshihiro-san can comment.
[1] http://marc.info/?l=linux-usb&m=149872369422476&w=2
Thanks,
Jack
drivers/usb/gadget/udc/core.c | 5 ++++-
include/linux/usb/gadget.h | 2 ++
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index e6f04ee..c1cef6a 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -812,6 +812,8 @@ int usb_gadget_map_request_by_dev(struct device *dev,
dev_err(dev, "failed to map buffer\n");
return -EFAULT;
}
+
+ req->dma_mapped = 1;
}
return 0;
@@ -836,9 +838,10 @@ void usb_gadget_unmap_request_by_dev(struct device *dev,
is_in ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
req->num_mapped_sgs = 0;
- } else {
+ } else if (req->dma_mapped) {
dma_unmap_single(dev, req->dma, req->length,
is_in ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
+ req->dma_mapped = 0;
}
}
EXPORT_SYMBOL_GPL(usb_gadget_unmap_request_by_dev);
diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
index 1a4a4ba..21468a7 100644
--- a/include/linux/usb/gadget.h
+++ b/include/linux/usb/gadget.h
@@ -48,6 +48,7 @@ struct usb_ep;
* by adding a zero length packet as needed;
* @short_not_ok: When reading data, makes short packets be
* treated as errors (queue stops advancing till cleanup).
+ * @dma_mapped: Indicates if request has been mapped to DMA (internal)
* @complete: Function called when request completes, so this request and
* its buffer may be re-used. The function will always be called with
* interrupts disabled, and it must not sleep.
@@ -103,6 +104,7 @@ struct usb_request {
unsigned no_interrupt:1;
unsigned zero:1;
unsigned short_not_ok:1;
+ unsigned dma_mapped:1;
void (*complete)(struct usb_ep *ep,
struct usb_request *req);
--
2.9.1.200.gb1ec08f
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