From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Vasut Date: Sun, 3 Jan 2016 10:35:06 +0100 Subject: [U-Boot] [PATCH] mvebu: usb: Add missing controller reset after initialization In-Reply-To: <20160103085923.B6C3038226E@gemini.denx.de> References: <20160102211834.E49A161C74@mail.nwl.cc> <20160103085923.B6C3038226E@gemini.denx.de> Message-ID: <201601031035.06649.marex@denx.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On Sunday, January 03, 2016 at 09:59:23 AM, Wolfgang Denk wrote: > Dear Phil, > > [added USB custodian to Cc:] Thanks > In message <20160102211834.E49A161C74@mail.nwl.cc> you wrote: > > In order to allow for Linux properly register the integrated EHCI host, > > we have to reset it after initialization. Without this, enumeration > > fails if 'usb start' wasn't issued prior to booting Linux. > > I think this reset should actually be done in the Linux driver. Correct. > From what you write I suspect that after a "usb stop" in U-Boot the > Linux driver maight fail, too. Leaving USB enabled in U-Boot is > extremely dangerous - see > > commit 3d71c81a9bb03f866a1e98da96363ef3f46c76b3 > Author: Markus Klotzb?cher > Date: Thu Jul 10 14:47:09 2008 +0200 > > USB: shutdown USB before booting > > This patch fixes a potentially serious issue related to USB which was > discouvered by Martin Krause and fixed for > ARM920T. Martin wrote: > > Turn off USB to prevent the host controller from writing to the > SDRAM while Linux is booting. This could happen, because the HCCA > (Host Controller Communication Area) lies within the SDRAM and the > host controller writes continously to this area (as busmaster!), for > example to increase the HccaFrameNumber variable, which happens > every 1 ms. > > This is a slightly modified version of the patch in order to shutdown > USB when booting on all architectures. > > Signed-off-by: Markus Klotzbuecher This reasoning is correct. Best regards, Marek Vasut