diff options
| author | Ming Lei <ming.lei@canonical.com> | 2011-08-31 00:03:13 +0800 |
|---|---|---|
| committer | Andrey Konovalov <andrey.konovalov@linaro.org> | 2012-02-14 23:03:46 +0400 |
| commit | 7f2be4a1c8181de24da244673b16ee98926b4a7e (patch) | |
| tree | ecbacdafd369e8e1869aa8fdf876c70e8d0812a4 | |
| parent | d65b4e98d7ea3038b767b70fe8be959b2913f16d (diff) | |
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.
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>
| -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 36ca5077cdf..7151535e887 100644 --- a/drivers/usb/host/ehci-q.c +++ b/drivers/usb/host/ehci-q.c @@ -1004,6 +1004,12 @@ 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; @@ -1091,6 +1097,18 @@ 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 0a5fda73b3f..01cefde1d49 100644 --- a/drivers/usb/host/ehci.h +++ b/drivers/usb/host/ehci.h @@ -746,6 +746,23 @@ 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 + /*-------------------------------------------------------------------------*/ #ifdef CONFIG_PCI |