From: Peter Chen <hzpeterchen@gmail.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Daewoong Kim <daewoong00.kim@lge.com>,
linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
allen.lkml@gmail.com, gustavoars@kernel.org,
a.darwish@linutronix.de, romain.perier@gmail.com,
dvyukov@google.com, andreyknvl@google.com,
mathias.nyman@intel.com, gregkh@linuxfoundation.org
Subject: Re: [PATCH 1/1] usb: xhci: setup packets don't need DMA mapping
Date: Fri, 15 Jan 2021 08:32:51 +0800 [thread overview]
Message-ID: <20210115003251.GA3443@b29397-desktop> (raw)
In-Reply-To: <20210114180021.GA1935@rowland.harvard.edu>
On 21-01-14 13:00:21, Alan Stern wrote:
> On Thu, Jan 14, 2021 at 01:04:02PM +0800, Peter Chen wrote:
> > On 21-01-14 11:59:07, Daewoong Kim wrote:
> > > DMA mapping of urb->setup_packet is not necessary for xHCI host
> > > controllers. The xHCI specification says that Setup Stage TRB includes
> > > whole Setup Data; therefore, urb->setup_dma will not be used in the xhci
> > > HCD code.
> > >
> >
> > How about bypass map/unmap operation for xHCI control transfer directly?
> >
> > diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> > index 91ab81c3fc79..0a0ab14b7638 100644
> > --- a/drivers/usb/host/xhci.c
> > +++ b/drivers/usb/host/xhci.c
> > @@ -1374,7 +1374,8 @@ static int xhci_map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb,
> >
> > xhci = hcd_to_xhci(hcd);
> >
> > - if (xhci_urb_suitable_for_idt(urb))
> > + if (xhci_urb_suitable_for_idt(urb) ||
> > + (usb_endpoint_xfer_control(&urb->ep->desc)))
> > return 0;
>
> Would this affect the map/unmap operations for the DATA packets in a
> control transfer, along with the SETUP packet?
>
Oh, you are right, Alan. We do need map/unmap operation for DATA
packet in control transfer.
--
Thanks,
Peter Chen
next prev parent reply other threads:[~2021-01-15 0:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-14 2:59 [PATCH 1/1] usb: xhci: setup packets don't need DMA mapping Daewoong Kim
2021-01-14 5:04 ` Peter Chen
2021-01-14 18:00 ` Alan Stern
2021-01-15 0:32 ` Peter Chen [this message]
2021-01-18 1:07 ` Daewoong Kim
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