Hi Markus,
On Thursday 10 July 2008, Markus Klotzbücher wrote:
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.
Yes, I remember hearing of this problem. I thought it was already fixed. Seems not to be the case. Please find a comment below.
Signed-off-by: Markus Klotzbuecher mk@denx.de
common/cmd_bootm.c | 18 ++++++++++++++++++ 1 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/common/cmd_bootm.c b/common/cmd_bootm.c
By implementing this usb_stop() in do_bootm() you prevent this problem in many cases (e.g. Linux booting). But unfortunately not in all cases. For example "bootelf" or "bootvx" are not fixed.
Can't this be solved in a different way. By calling usb_stop each time after an USB command completes. IIRC, this is how it is done in the U-Boot network implementation too.
What do you think?
Best regards, Stefan
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