Hi, I have a missing urb completion problem on ARMv7 based platform. I thought the above problem was caused by coherent memory between the EHCI device and CPU so I tryied to allocates device type memory for EHCI via dma_declare_coherent_memory at machine initialization step so that EHCI always allocates from those device type memory. It seems to solve the issue because I didn't see any problem. But I am not sure it is acceptable solution. So I applied the patch https://lkml.org/lkml/2011/8/31/344. But it could not solve the problem so that I added another wmb() as my patch, and now my platform works fine. I am not sure what's the exact problem and what wmb I added could solve but I just think the problem is related to store buffer flush of hw_next. Anyway, important thing is that it fixed my problem so I expect you expert guys could find what I am missing and a right solution. IMHO, the patch might miss updating hw_next pointer. Am I correct? I understand the wmb() is just memory barrier, not write-buffer flush. But it is true that wmb() can flush write buffer in ARM. Anyhow I think that memory type, "normal memory, non-cacheable", may have a problem for some devices that needs device type memory. I cannot get conclusion from the discussion at https://lkml.org/lkml/2011/8/31/344. Which can I do for my platform, wmb() or dma_coherent_write_sync()? Signed-off-by: Gioh Kim <gioh.kim@xxxxxxx> --- drivers/usb/host/ehci-q.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c index d34b399..779d9e8 100644 --- a/drivers/usb/host/ehci-q.c +++ b/drivers/usb/host/ehci-q.c @@ -501,6 +501,7 @@ qh_completions (struct ehci_hcd *ehci, struct ehci_qh *qh) last = list_entry (qtd->qtd_list.prev, struct ehci_qtd, qtd_list); last->hw_next = qtd->hw_next; + wmb(); } /* remove qtd; it's recycled after possible urb completion */ -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
