From patchwork Tue Aug 30 16:03:13 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 1113322 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter2.kernel.org (8.14.4/8.14.4) with ESMTP id p7UG3VwP025514 for ; Tue, 30 Aug 2011 16:03:31 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754997Ab1H3QD2 (ORCPT ); Tue, 30 Aug 2011 12:03:28 -0400 Received: from mail-qy0-f181.google.com ([209.85.216.181]:48267 "EHLO mail-qy0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751317Ab1H3QD2 (ORCPT ); Tue, 30 Aug 2011 12:03:28 -0400 Received: by qyk34 with SMTP id 34so4628208qyk.19 for ; Tue, 30 Aug 2011 09:03:27 -0700 (PDT) Received: by 10.142.239.3 with SMTP id m3mr3398475wfh.230.1314720207121; Tue, 30 Aug 2011 09:03:27 -0700 (PDT) Received: from localhost ([183.37.203.48]) by mx.google.com with ESMTPS id w18sm4139892wfg.21.2011.08.30.09.03.20 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 30 Aug 2011 09:03:26 -0700 (PDT) From: ming.lei@canonical.com To: greg@kroah.com, stern@rowland.harvard.edu Cc: linux-usb@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-omap@vger.kernel.org, Ming Lei , Russell King Subject: [PATCH] usb: ehci: make HC see up-to-date qh/qtd descriptor ASAP Date: Wed, 31 Aug 2011 00:03:13 +0800 Message-Id: <1314720193-26577-1-git-send-email-ming.lei@canonical.com> X-Mailer: git-send-email 1.7.4.1 Sender: linux-omap-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter2.kernel.org [140.211.167.43]); Tue, 30 Aug 2011 16:03:31 +0000 (UTC) From: Ming Lei 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. Cc: Alan Stern Cc: Russell King Signed-off-by: Ming Lei Signed-off-by: Alan Stern --- drivers/usb/host/ehci-q.c | 18 ++++++++++++++++++ drivers/usb/host/ehci.h | 17 +++++++++++++++++ 2 files changed, 35 insertions(+), 0 deletions(-) diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c index 0917e3a..2719879 100644 --- a/drivers/usb/host/ehci-q.c +++ b/drivers/usb/host/ehci-q.c @@ -995,6 +995,12 @@ static void qh_link_async (struct ehci_hcd *ehci, struct ehci_qh *qh) head->qh_next.qh = qh; head->hw->hw_next = dma; + /* + * flush qh descriptor into memory immediately, + * see comments in qh_append_tds. + * */ + ehci_sync_mem(); + qh_get(qh); qh->xacterrs = 0; qh->qh_state = QH_STATE_LINKED; @@ -1082,6 +1088,18 @@ static struct ehci_qh *qh_append_tds ( wmb (); dummy->hw_token = token; + /* + * Writing to dma coherent buffer on ARM may + * be delayed to reach memory, so HC may not see + * hw_token of dummy qtd in time, which can cause + * the qtd transaction to be executed very late, + * and degrade performance a lot. ehci_sync_mem + * is added to flush 'token' immediatelly into + * memory, so that ehci can execute the transaction + * ASAP. + * */ + ehci_sync_mem(); + urb->hcpriv = qh_get (qh); } } diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h index cc7d337..313d9d6 100644 --- a/drivers/usb/host/ehci.h +++ b/drivers/usb/host/ehci.h @@ -738,6 +738,23 @@ static inline u32 hc32_to_cpup (const struct ehci_hcd *ehci, const __hc32 *x) #endif +/* + * Writing to dma coherent memory on ARM may be delayed via L2 + * writing buffer, so introduce the helper which can flush L2 writing + * buffer into memory immediately, especially used to flush ehci + * descriptor to memory. + * */ +#ifdef CONFIG_ARM_DMA_MEM_BUFFERABLE +static inline void ehci_sync_mem() +{ + mb(); +} +#else +static inline void ehci_sync_mem() +{ +} +#endif + /*-------------------------------------------------------------------------*/ #ifndef DEBUG