linux-kernel - Re: Initialisation of SOC USB pads

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Date:   Wed, 22 May 2019 17:40:19 +0300
From:   Igor Plyatov <plyatov@...il.com>
To:     linux-usb@...r.kernel.org
Cc:     Alan Stern <stern@...land.harvard.edu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Initialisation of SOC USB pads

Hi!

Topic update...

USB pads operate. I see USB traffic on the bus by Logical analyzer.

This is definitely Linux kernel issue, because USB works fine at U-Boot, 
when I try to load kernel image and device tree from USB disk.

Additionally, USB works on same board with old Linux kernel 2.6.39.

Current Linux kernel (4.9.52), has issue with USB speed on AT91SAM9G20. 
I see different USB speeds in U-Boot and in Linux-4.9.52. U-Boot has 12 
MHz USB speed, while Linux-4.9.52 has 6 MHz USB speed.

I guess, what need to be changed to have correct USB speed?

I have attached resulting Device Tree source code, if it can be useful.

Best wishes.
--
Igor Plyatov


13.05.2019 18:39, Igor Plyatov пишет:
> 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.
>
> Best wishes
> -- 
> Igor Plyatov
>

Download attachment "device-tree.dts" of type "audio/vnd.dts" (30531 bytes)