diff options
| author | Ming Lei <ming.lei@canonical.com> | 2011-08-30 16:03:13 +0000 |
|---|---|---|
| committer | Benoit Goby <benoit@android.com> | 2011-09-06 17:40:39 -0700 |
| commit | 95cf7a199cf8bcd6647c3b90efb78614157bf766 (patch) | |
| tree | bf71c1c9a80c8d74b479f9a68a3b9132947c38a5 /drivers/usb | |
| parent | 7013f4976374ea75cb35446393be7bdc37bf607f (diff) | |
| download | kernel_samsung_tuna-95cf7a199cf8bcd6647c3b90efb78614157bf766.zip kernel_samsung_tuna-95cf7a199cf8bcd6647c3b90efb78614157bf766.tar.gz kernel_samsung_tuna-95cf7a199cf8bcd6647c3b90efb78614157bf766.tar.bz2 | |
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>
Diffstat (limited to 'drivers/usb')
| -rw-r--r-- | drivers/usb/host/ehci-q.c | 18 | ||||
| -rw-r--r-- | 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 989e0a8..9706c2b 100644 --- a/drivers/usb/host/ehci.h +++ b/drivers/usb/host/ehci.h @@ -736,6 +736,23 @@ 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 |