usb: ehci: make HC see up-to-date qh/qtd descriptor ASAP
authorMing Lei <ming.lei@canonical.com>
Tue, 30 Aug 2011 16:03:13 +0000 (16:03 +0000)
committerDan Willemsen <dwillemsen@nvidia.com>
Thu, 1 Dec 2011 05:39:03 +0000 (21:39 -0800)
commit010cd2ec863a14f5265c07332550d6f0bf8d1956
tree735fb55e1edaf4dbb899aa9fef554f320d80ec98
parentdfd3a1b588094da9140cdfb80cf9005bfe41b99e
usb: ehci: make HC see up-to-date qh/qtd descriptor ASAP

This patch introduces the helper of ehci_sync_mem to flush
qtd/qh into memory immediately on some ARM, so that HC can
see the up-to-date qtd/qh descriptor asap.

This patch fixs one performance bug on ARM Cortex A9 dual core
platform, which has been reported on quite a few ARM machines
(OMAP4, Tegra 2, snowball...), see details from link of
https://bugs.launchpad.net/bugs/709245.

The patch has been tested ok on OMAP4 panda A1 board, and the
performance of 'dd' over usb mass storage can be increased from
4~5MB/sec to 14~16MB/sec after applying this patch.

Change-Id: I7994c58a1001c7f46f13e09420328a3916bbfcef
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
drivers/usb/host/ehci-q.c
drivers/usb/host/ehci.h