Messages in this thread | | | Subject | Re: [PATCH v5 1/2] usbip: Skip DMA mapping and unmapping for urb at vhci | From | shuah <> | Date | Tue, 13 Aug 2019 12:34:55 -0600 |
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On 8/8/19 10:18 AM, shuah wrote: > On 8/8/19 9:54 AM, Suwan Kim wrote: >> vhci doesn’t do DMA for remote device. Actually, the real DMA >> operation is done by network card driver. vhci just passes virtual >> address of the buffer to the network stack, so vhci doesn’t use and >> need dma address of the buffer of the URB. >> >> But HCD provides DMA mapping and unmapping function by default. >> Moreover, it causes unnecessary DMA mapping and unmapping which >> will be done again at the NIC driver and it wastes CPU cycles. >> So, implement map_urb_for_dma and unmap_urb_for_dma function for >> vhci in order to skip the DMA mapping and unmapping procedure. >> >> When it comes to supporting SG for vhci, it is useful to use native >> SG list (urb->num_sgs) instead of mapped SG list because DMA mapping >> fnuction can adjust the number of SG list (urb->num_mapped_sgs). >> And vhci_map_urb_for_dma() prevents isoc pipe from using SG as >> hcd_map_urb_for_dma() does. >> >> Signed-off-by: Suwan Kim <suwan.kim027@gmail.com> >> --- >> v4 - v5 >> - Replace pr_err() with dev_err() in the error path. >> >> v3 - v4 >> - Replace WARN_ON() with pr_err() in the error path. >> >> v2 - v3 >> - Move setting URB_DMA_MAP_SG flag to the patch 2. >> - Prevent isoc pipe from using SG buffer. >> >> v1 - v2 >> - Add setting URB_DMA_MAP_SG flag in urb->transfer_flags to tell >> stub driver to use SG buffer. >> --- >> drivers/usb/usbip/vhci_hcd.c | 19 +++++++++++++++++++ >> 1 file changed, 19 insertions(+) >> >> diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c >> index 000ab7225717..ea82b932a2f9 100644 >> --- a/drivers/usb/usbip/vhci_hcd.c >> +++ b/drivers/usb/usbip/vhci_hcd.c >> @@ -1288,6 +1288,22 @@ static int vhci_free_streams(struct usb_hcd >> *hcd, struct usb_device *udev, >> return 0; >> } >> +static int vhci_map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb, >> + gfp_t mem_flags) >> +{ >> + if (usb_endpoint_xfer_isoc(&urb->ep->desc) && urb->num_sgs) { >> + dev_err(&urb->dev->dev, "SG is not supported for isochronous >> transfer\n"); >> + return -EINVAL; >> + } >> + >> + return 0; >> +} >> + >> +static void vhci_unmap_urb_for_dma(struct usb_hcd *hcd, struct urb *urb) >> +{ >> + dev_dbg(hcd->self.controller, "vhci does not unmap urb for dma\n"); >> +} >> + >> static const struct hc_driver vhci_hc_driver = { >> .description = driver_name, >> .product_desc = driver_desc, >> @@ -1304,6 +1320,9 @@ static const struct hc_driver vhci_hc_driver = { >> .get_frame_number = vhci_get_frame_number, >> + .map_urb_for_dma = vhci_map_urb_for_dma, >> + .unmap_urb_for_dma = vhci_unmap_urb_for_dma, >> + >> .hub_status_data = vhci_hub_status, >> .hub_control = vhci_hub_control, >> .bus_suspend = vhci_bus_suspend, >> > > Looks good to me. > > Reviewed-by: Shuah Khan <skhan@linuxfoundation.org> >
Greg!
Please pick this one up.
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
thanks, -- Shuah
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