On Wed, Oct 09, 2019 at 06:39:00PM -0500, Rob Herring wrote: > 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. Given that support for gen 2 speeds is dependent on signal trace length, it doesn't really make sense to restrict the whole controller to a given speed if only the signal trace for a single port exceeds the limit for which gen 2 would work. Also, the USB PHYs are in a different hardware block than the USB controller, so this really is a property of the PHY block, not the USB controller. Thierry
Attachment:
signature.asc
Description: PGP signature
