From: Hans Petter Selasky <h...@selasky.org>
Subject: Re: About XHCI_TD_PAGE_SIZE.
Date: Sat, 20 Dec 2014 10:30:36 +0100
> On 12/17/14 05:42, Nidal Khalil wrote:
>> I agree. Thanks
>> On Dec 16, 2014 6:25 PM, "Kohji Okuno" <okuno.ko...@jp.panasonic.com> wrote:
>>> Hi Hans,
>>> If we use PAGE_SIZE as USB_PAGE_SIZE, we should use PAGE_SIZE as
>>> XHCI_TD_PAGE_SIZE, too. I think.
>>> As you know, one TRB can use 1~64kB for the transfer length.
> We currently only check if 4K pages are supported by the hardware. If you
> change the value of XHCI_TD_PAGE_SIZE, you will also need to change the checks
> other places. You know that PAGE_SIZE is not a constant?
> Do you have a complete patch?
XHCI_TD_PAGE_SIZE is used at only 2-points.
1. use as XHCI_TD_PAYLOAD_MAX (XHCI_TD_PAGE_NBUF) in xhci.h
We sholud change as the following, I think.
- #define XHCI_TD_PAGE_NBUF 17 /* units, room enough for 64Kbytes */
- #define XHCI_TD_PAGE_SIZE 4096 /* bytes */
- #define XHCI_TD_PAYLOAD_MAX (XHCI_TD_PAGE_SIZE * (XHCI_TD_PAGE_NBUF - 1))
+ #define XHCI_TD_PAYLOAD_MAX (64*1024) /* bytes */
+ #define XHCI_TD_PAGE_SIZE PAGE_SIZE /* bytes */
+ /* units, room enough for 64Kbytes */
+ #define XHCI_TD_PAGE_NBUF (XHCI_TD_PAYLOAD_MAX/XHCI_TD_PAGE_SIZE + 1)
2. use as the maximum length of TRB.
If PAGE_SIZE is 8kB, buf_res.length may be 8kB.
But, we can set 1B~64kB for length of TRB. This is the spcification
of xHCI. So, we don't need change this point.
1807 /* check for maximum length */
1808 if (buf_res.length > XHCI_TD_PAGE_SIZE)
1809 buf_res.length = XHCI_TD_PAGE_SIZE;
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