Re: [PATCH 00/12] usb: early: add support for early printk through USB3 debug port

[Dave Young]

On 10/28/15 at 04:00pm, Lu Baolu wrote:
> This patch series adds support for early printk through USB3 debug port.
> USB3 debug port is described in xHCI specification as an optional extended
> capability.
> 
> The first patch adds a file in debugfs, through which users can check
> whether the debug capability is supported by a specific host controller.
> 
> Patch 2 to 10 add the driver for xHCI debug capability. It interfaces with
> the register set and provides the required ops (read/write/control) to upper
> layers. Early printk is one consumer of these ops. The hooks for early printk
> are introduced in patch 9. This design is similar to what we have done in
> drivers/usb/early/ehci-dbgp.c.
> 
> Patch 11 is a minor change to usb_debug module. This change is required to
> bind usb_debug with the USB3 debug device.
> 
> Patch 12 is the design document and user guide.
> 

Nice work, I want to try your patches. But I have only one machine with
debug capability, I think I can use it as debug target. Can I use another
machine with usb 3.0 but no debug capability as the debug host?

BTW, I hacked a cable according to usb 3 spec, cut vbus/d+/d-, cross wired
ss pins.

Thanks
Dave
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