On Wed, 31 Aug 2011 ming.lei@xxxxxxxxxxxxx wrote: > From: Ming Lei <ming.lei@xxxxxxxxxxxxx> > > 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 <stern@xxxxxxxxxxxxxxxxxxx> > Cc: Russell King <linux@xxxxxxxxxxxxxxxx> > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx> > --- > 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. > + * */ Comments are supposed to look like this: /* * Blah blah blah * blah blah blah */ > + 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. > + * */ Here too. > + 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. > + * */ And here. > +#ifdef CONFIG_ARM_DMA_MEM_BUFFERABLE > +static inline void ehci_sync_mem() > +{ > + mb(); > +} > +#else > +static inline void ehci_sync_mem() > +{ > +} > +#endif > + Except for the formatting of the comments, this is fine. When you fix up the comments, you can add: Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
