Hi, > -----Original Message----- > From: Alan Stern [mailto:st...@rowland.harvard.edu] > Sent: Saturday, March 18, 2017 12:44 AM > To: Lipengcheng > Cc: gre...@linuxfoundation.org; linux-...@vger.kernel.org; > linux-kernel@vger.kernel.org > Subject: Re: EHCI > > On Fri, 17 Mar 2017, Lipengcheng wrote: > > > Hi, > > In the ehci-hub.c,the ehci_handshake(ehci, status_reg, PORT_RESET, 0, > > 1000) use that the timeout is 1000us. The 1000us timeout can not > > satisfy all the chips. The EHCI protocol describes:A host controller > > must terminate the reset and stabilize the state of the port within 2 > > milliseconds of software transitioning this bit from a one to a zero. > > So I think timeout time is set to 2000us more appropriate. If I set > > the timeout time is set to 2000us and may it produce side effects? > > That is a long time to wait with interrupts disabled. You probably should > release the spinlock and enable interrupts during the handshake. > > Have you seen any errors with the current 1000 us value? If you haven't, > there's no reason to change the code. > Yes, I have some error -110(-ETIMEDOUT) with the current 1000us value. When I set the value 2000us, it is ok. > Alan Stern
Best Regards, Pengcheng Li
