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| author | Nicolas Saenz Julienne <nsaenzjulienne@suse.de> | 2019-04-26 16:23:29 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-04-27 15:53:58 +0300 |
| commit | 33e39350ebd20fe6a77a51b8c21c3aa6b4a208cf (patch) | |
| tree | f39027fadd5dee7fd06773613f20c429ce3a90e1 /drivers/usb/host/xhci-ring.c | |
| parent | 95e060e68bd98f28763adbc311797eebc4d31e0c (diff) | |
| download | linux-33e39350ebd20fe6a77a51b8c21c3aa6b4a208cf.tar.xz | |
usb: xhci: add Immediate Data Transfer support
Immediate data transfers (IDT) allow the HCD to copy small chunks of
data (up to 8bytes) directly into its output transfer TRBs. This avoids
the somewhat expensive DMA mappings that are performed by default on
most URBs submissions.
In the case an URB was suitable for IDT. The data is directly copied
into the "Data Buffer Pointer" region of the TRB and the IDT flag is
set. Instead of triggering memory accesses the HC will use the data
directly.
The implementation could cover all kind of output endpoints. Yet
Isochronous endpoints are bypassed as I was unable to find one that
matched IDT's constraints. As we try to bypass the default DMA mappings
on URB buffers we'd need to find a Isochronous device with an
urb->transfer_buffer_length <= 8 bytes.
The implementation takes into account that the 8 byte buffers provided
by the URB will never cross a 64KB boundary.
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Reviewed-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/host/xhci-ring.c')
| -rw-r--r-- | drivers/usb/host/xhci-ring.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index 9215a28dad40..28250319d0b8 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -3275,6 +3275,12 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags, field |= TRB_IOC; more_trbs_coming = false; td->last_trb = ring->enqueue; + + if (xhci_urb_suitable_for_idt(urb)) { + memcpy(&send_addr, urb->transfer_buffer, + trb_buff_len); + field |= TRB_IDT; + } } /* Only set interrupt on short packet for IN endpoints */ @@ -3414,6 +3420,12 @@ int xhci_queue_ctrl_tx(struct xhci_hcd *xhci, gfp_t mem_flags, if (urb->transfer_buffer_length > 0) { u32 length_field, remainder; + if (xhci_urb_suitable_for_idt(urb)) { + memcpy(&urb->transfer_dma, urb->transfer_buffer, + urb->transfer_buffer_length); + field |= TRB_IDT; + } + remainder = xhci_td_remainder(xhci, 0, urb->transfer_buffer_length, urb->transfer_buffer_length, |