linux-kernel - Re: [PATCH v4 3/5] dt-bindings: phy: tegra: Add Tegra194 support

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Message-ID: <20191009233900.GA9109@bogus>
Date:   Wed, 9 Oct 2019 18:39:00 -0500
From:   Rob Herring <robh@...nel.org>
To:     JC Kuo <jckuo@...dia.com>
Cc:     gregkh@...uxfoundation.org, thierry.reding@...il.com,
        jonathanh@...dia.com, kishon@...com, linux-tegra@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, nkristam@...dia.com
Subject: Re: [PATCH v4 3/5] dt-bindings: phy: tegra: Add Tegra194 support

On Wed, Oct 09, 2019 at 10:43:41AM +0800, JC Kuo wrote:
> Extend the bindings to cover the set of features found in Tegra194.
> Note that, technically, there are four more supplies connected to the
> XUSB pad controller (DVDD_PEX, DVDD_PEX_PLL, HVDD_PEX and HVDD_PEX_PLL)
> , but the power sequencing requirements of Tegra194 require these to be
> under the control of the PMIC.
> 
> Tegra194 XUSB PADCTL supports up to USB 3.1 Gen 2 speed, however, it is
> possible for some platforms have long signal trace that could not
> provide sufficient electrical environment for Gen 2 speed. To deal with
> this, a new device node property "nvidia,disable-gen2" was added to
> Tegra194 that be used to specifically disable Gen 2 speed for a
> particular USB 3.0 port so that the port can be limited to Gen 1 speed
> and avoid the instability.

I suspect this may be a common issue and we should have a common 
property. Typically, this kind of property is in the controller though 
and supports multiple speed limits. See PCI bindings for inspiration.

Rob