Messages in this thread | | | Subject | Re: [PATCH v2 1/2] usbip: Skip DMA mapping and unmapping for urb at vhci | From | shuah <> | Date | Mon, 22 Jul 2019 14:26:42 -0600 |
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Hi Suwan,
On 7/5/19 10:43 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. > > 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). > > 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. > > To support SG, vhci_map_urb_for_dma() sets URB_DMA_MAP_SG flag in > urb->transfer_flags if URB has SG list and this flag will tell the > stub driver to use SG list. > > Signed-off-by: Suwan Kim <suwan.kim027@gmail.com> > --- > 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..14fc6d9f4e6a 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) > +{ > + dev_dbg(hcd->self.controller, "vhci does not map urb for dma\n"); > + > + if (urb->num_sgs) > + urb->transfer_flags |= URB_DMA_MAP_SG; > +
Shouldn't this be part of patch 2. The debug message saying "no map" and setting flag doesn't make sense.
> + return 0;
This should be a tab and no spaces btw. chekpatch isn't happy.
> +} > + > +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");
This should be a tab and no spaces btw. chekpatch isn't happy.
WARNING: please, no spaces at the start of a line #144: FILE: drivers/usb/usbip/vhci_hcd.c:1299: + return 0;$
WARNING: please, no spaces at the start of a line #149: FILE: drivers/usb/usbip/vhci_hcd.c:1304: + dev_dbg(hcd->self.controller, "vhci does not unmap urb for dma\n");$
total: 0 errors, 2 warnings, 31 lines checked
> +} > + > 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, >
thanks, -- Shuah
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