From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfgang Grandegger Date: Tue, 20 Dec 2011 17:10:28 +0100 Subject: [U-Boot] [PATCH] ehci: speed up initialization In-Reply-To: References: <1323125542-6286-1-git-send-email-vpalatin@chromium.org> <4EEF290B.9060106@grandegger.com> <4EEF3CBA.5080404@grandegger.com> Message-ID: <4EF0B374.10908@grandegger.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 12/19/2011 05:59 PM, Remy Bohmer wrote: > Hi Wolfgang, > > 2011/12/19 Wolfgang Grandegger : >> On 12/19/2011 01:51 PM, Vincent Palatin wrote: >>> On Mon, Dec 19, 2011 at 04:07, Wolfgang Grandegger wrote: >>>> I just realized that this patch breaks "usb start" on my mx53loco board: >>>> >>>> The device is not found at the first attempt. Obviously, a value of 10 >>>> for bPwrOn2PwrGood seems too short but 20 works fine. Would that be a >>>> resonable compromise? If yes, I could send a patch. >>> >>> This doesn't match the EHCI standard which explicity states that the >>> power should be good after 20ms (paragraph 2.3.9 in EHCI 1.0), so we >>> should probably find whether we are missing another delay somewhere in >>> the generic EHCI code (which used to be hidden and should be fixed) or >>> if i.MX53 is not compliant with the standard and need a special quirk. >> >> I'm not an USB expert but if I look into the hub_power_on() function of >> the Linux kernel it waits at least 100ms (and only once). See: >> >> http://lxr.linux.no/#linux+v3.1.5/drivers/usb/core/hub.c#L567 > > I would prefer a solution in line with the specification, but what is > the reason why Linux takes 100 msec here? > Is that just chosen randomly , or was there a good reason for it? > If there is a good reason (which I assume) I would prefer to follow > Linux here and go for the 100 msec. > > Can you please provide a patch? OK, should find time tomorrow. Wolfgang.