[U-Boot] [PATCH 18/20] x86: minnowmax: Add a environment variable for USB power-on delay

[Simon Glass]

On 16 June 2017 at 07:31, Bin Meng <bmeng.cn at gmail.com> wrote:
> Occasionally it was observed that on Intel MinnowMax board, with a
> USB 2.0 device connected to the bottom port, when doing 'usb start'
> on the xHCI controller:
>
>   scanning bus 0 for devices... cannot reset port 3!?
>
> But neither of the two USB ports is routed to xHCI root port 3.
> Adding some debug information shows that xHCI port 3 PORTSC register
> mysteriously reports both CCS = 1 and CSC = 1.
>
> This is not seen every time. After increasing the timeout to wait
> for power to become stable, the issue is gone. So this indicates
> current default USB power-on delay (20ms) might be at a critical
> region where power is stable/unstable. U-Boot provides a mechanism
> to have a environment variable to override the default one. Add
> one for MinnowMax.
>
> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
> ---
>
>  include/configs/minnowmax.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Reviewed-by: Simon Glass <sjg at chromium.org>