Re: Fix for slow run(4) configuration on OHCI/UHCI

[christos%astron.com@localhost (Christos Zoulas)]

In article <24273.15131.928644.743625%guava.gson.org@localhost>,
Andreas Gustafsson  <gson%gson.org@localhost> wrote:
>Hi all,
>
>When I connect a USB WiFi adapter based on a Ralink RT5370 chip to a
>USB port that uses an OHCI or UHCI host controller, running "ifconfig
>run0 up" takes a very long time, about 20-30 seconds.
>
>This is because the run(4) driver writes a large amount of data to the
>device just two bytes at a time using the WRITE_2 command, and each
>write takes two full USB frames of 1 millisecond each on UHCI, or
>three frames on OCHI.  With an EHCI or XHCI controller, the large
>number of transfers is not a problem as these controllers can perform
>multiple control transfers within a single frame.
>
>The driver already contains code to do the transfers in larger blocks
>using the WRITE_REGION_1 command, but it's #if'ed out with a comment
>saying it is "not stable on RT2860".  The FreeBSD driver is similar,
>except that its version of the #if'ed-out code limits the transfers
>to a maximum of 64 bytes at a time.
>
>I have verified that enabling the use of WRITE_REGION_1 with the
>64-bit limit from FreeBSD works with my RT5370 based adapter, and
>makes it configure about ten times faster on OHCI and UHCI.
>
>I'm now using the following patch, which enables the use of
>WRITE_REGION_1 using blocks of up to 64 bytes for the RT5370 only:
>
>  https://www.gson.org/netbsd/patches/run-faster.patch
>
>OK to commit?

Yes, let's do it but put a comment in the commit message that provides
a summary of this message, so next time someone encounters an issue,
they find the information in one place.

christos