From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Lindgren Subject: [PATCH 2/2] usb: musb: Tiny dma in transfers won't complete with cpp41 Date: Wed, 18 Jan 2017 16:49:18 -0800 Message-ID: <20170119004918.9986-3-tony@atomide.com> References: <20170119004918.9986-1-tony@atomide.com> Return-path: In-Reply-To: <20170119004918.9986-1-tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Bin Liu Cc: Alexandre Bailon , Andreas Kemnade , Boris Brezillon , Felipe Balbi , George Cherian , Greg Kroah-Hartman , Grygorii Strashko , Kishon Vijay Abraham I , Ivaylo Dimitrov , Johan Hovold , Ladislav Michl , Laurent Pinchart , Sergei Shtylyov , linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-omap@vger.kernel.org At least with the cppi41 dma, size 1 in dma transfers will just wait until the device is disconnected. And it also seems that enumerating a USB stick with a hub can take a USB reset with smallish size in transfers. This causes timeouts in cppi41 dma runtime PM. Fix the issue by adding a minimum size of 16 which is based on my obeservations on BeagleBone to make enumerating more reliable. Fixes: fdea2d09b997 ("dmaengine: cppi41: Add basic PM runtime support") Signed-off-by: Tony Lindgren --- drivers/usb/musb/musb_host.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c --- a/drivers/usb/musb/musb_host.c +++ b/drivers/usb/musb/musb_host.c @@ -743,7 +743,14 @@ static void musb_ep_program(struct musb *musb, u8 epnum, musb_ep_select(mbase, epnum); - if (is_out && !len) { + /* + * Skip dma for zero sized out and small in transfers. + * At least cppi41 in dma will just hang with size of 1 until the + * device is connected. For sizes 8 and less it seems to take a + * long time to complete. Let's use minimum size of 16 to avoid + * tiny in DMA transfers. + */ + if ((is_out && !len) || (!is_out && (len < 16))) { use_dma = 0; csr = musb_readw(epio, MUSB_TXCSR); csr &= ~MUSB_TXCSR_DMAENAB; -- 2.11.0 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html