linux-kernel - Re: Initialisation of SOC USB pads

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Date:   Mon, 13 May 2019 11:47:40 -0400 (EDT)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Igor Plyatov <plyatov@...il.com>
cc:     linux-usb@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Initialisation of SOC USB pads

On Mon, 13 May 2019, Igor Plyatov wrote:

> Dear developers,
> 
> can you please explain who must configure AT91SAM9G20 SOC pads to 
> operate as USB Host port? Is it AT91Bootstrap, U-Boot bootloader, Linux 
> kernel or this is not required at all?
> 
> I ask, because during connection of USB disk, my board complains
> 
> usb 1-1: device descriptor read/64, error -62
> usb 1-1: device descriptor read/64, error -62
> usb 1-1: device descriptor read/64, error -62
> usb 1-1: device descriptor read/64, error -62
> usb 1-1: device not accepting address 4, error -62
> usb 1-1: device not accepting address 5, error -62
> usb usb1-port1: unable to enumerate USB device
> 
> 
> Looks like there is no connectivity between USB Host module of SOC and 
> USB device. Or am I wrong?
> 
> 
> My setup is:
> 
> 
> * AT91SAM9G20 based custom board;
> * Linux kernel 4.9.36, from LINUX4SAM project.
> * USB disk connected to USB Host port 0 (HDPA, HDMA pins of SOC). 39 Ohm 
> series resistors and 15 Kohm pull-down resistors added at these lines. 
> Connectivity between SOC and USB device confirmed by Ohmmeter.
> * USB_VBUS voltage measured at USB connector = 4.96 VDC.

You probably should ask somebody at the LINUX4SAM project.

Alan Stern