Dear Phil,
[added USB custodian to Cc:]
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.
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 mk@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.krause@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 mk@denx.de
Best regards,
Wolfgang Denk