On Sunday, January 03, 2016 at 09:59:23 AM, Wolfgang Denk wrote: > Dear Phil, > > [added USB custodian to Cc:]
Thanks > In message <20160102211834.e49a161...@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 Klotzbücher <m...@denx.de> > 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 <martin.kra...@tqs.de> 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 <m...@denx.de> This reasoning is correct. Best regards, Marek Vasut _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot