From: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
To: Ran Wang <ran.wang_1@nxp.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Felipe Balbi <balbi@kernel.org>, Yang Li <pku.leo@gmail.com>
Cc: linux-usb@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [RESEND][PATCH v3 1/2] usb: dwc3: Add avoiding vbus glitch happen during xhci reset
Date: Thu, 6 Jun 2019 11:16:54 +0300 [thread overview]
Message-ID: <78eb1558-b8d4-0632-ad0c-4144c711d2da@cogentembedded.com> (raw)
In-Reply-To: <20190606025418.26313-1-ran.wang_1@nxp.com>
Hello!
On 06.06.2019 5:54, Ran Wang wrote:
> When DWC3 is set to host mode by programming register DWC3_GCTL, VBUS
> (or its control signal) will turn on immediately on related Root Hub
> ports. Then the VBUS will be de-asserted for a little while during xhci
> reset (conducted by xhci driver) for a little while and back to normal.
>
> This VBUS glitch might cause some USB devices emuration fail if kernel
Enumeration. :-)
> boot with them connected. One SW workaround which can fix this is to
> program all PORTSC[PP] to 0 to turn off VBUS immediately after setting
> host mode in DWC3 driver(per signal measurement result, it will be too
> late to do it in xhci-plat.c or xhci.c).
>
> Signed-off-by: Ran Wang <ran.wang_1@nxp.com>
> Reviewed-by: Rob Herring <robh@kernel.org>
[...]
MBR, Sergei
next prev parent reply other threads:[~2019-06-06 8:16 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-06 2:54 [RESEND][PATCH v3 1/2] usb: dwc3: Add avoiding vbus glitch happen during xhci reset Ran Wang
2019-06-06 2:54 ` [RESEND][PATCH v3 2/2] usb: dwc3: Add workaround for host mode VBUS glitch when boot Ran Wang
2019-06-06 8:16 ` Sergei Shtylyov [this message]
2019-06-06 8:20 ` [RESEND][PATCH v3 1/2] usb: dwc3: Add avoiding vbus glitch happen during xhci reset Ran Wang
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