From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: Re: [PATCH v4 3/5] dt-bindings: phy: tegra: Add Tegra194 support Date: Thu, 17 Oct 2019 13:44:10 +0200 Message-ID: <20191017114410.GD3122066@ulmo> References: <20191009024343.30218-1-jckuo@nvidia.com> <20191009024343.30218-4-jckuo@nvidia.com> <20191009233900.GA9109@bogus> <20191014131752.GF422231@ulmo> <57692050-8284-a31f-71fd-7441823f3f2b@nvidia.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="4zI0WCX1RcnW9Hbu" Return-path: Content-Disposition: inline In-Reply-To: <57692050-8284-a31f-71fd-7441823f3f2b@nvidia.com> Sender: linux-kernel-owner@vger.kernel.org To: JC Kuo Cc: Rob Herring , Greg Kroah-Hartman , Jon Hunter , Kishon Vijay Abraham I , linux-tegra@vger.kernel.org, Linux USB List , "linux-kernel@vger.kernel.org" , devicetree@vger.kernel.org, Nagarjuna Kristam List-Id: linux-tegra@vger.kernel.org --4zI0WCX1RcnW9Hbu Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Oct 17, 2019 at 03:48:52PM +0800, JC Kuo wrote: > Hi Thierry, Hi Rob, Hi Kishon, > Please let me know your thoughts of the below implementation. >=20 > 1. Add a "bool disable_gen2" to "phy->attrs" structure. phy->attrs is pretty bus agnostic, so adding a USB-specific property doesn't sound like the right thing to do here. > 2. In _of_phy_get() of phy-core.c to add the follow to parse a generic pr= operty. >=20 > phy->attrs.disable_gen2 =3D of_property_read_bool(args.np, > "usb-disable-gen2"); > 3. In individual phy driver, to add SOC/PHY specific programming accordin= gly. Could this perhaps be done using the ->set_mode() callback? We don't currently implement that, but we could implement it and then perhaps use the submode parameter to distinguish between USB 3.1 Gen 1 and USB 3.1 Gen 2. Perhaps a good mapping would look like this: USB 3.1 Gen 1: mode =3D PHY_MODE_USB_HOST_SS, submode =3D 0x0300 USB 3.1 Gen 2: mode =3D PHY_MODE_USB_HOST_SS, submode =3D 0x0301 The above basically reflects that USB 3.1 Gen 1 is really USB 3.0. This would also work with other speeds: USB 2.0: mode =3D PHY_MODE_USB_HOST_HS, submode =3D 0x0200 etc. I suppose to make this clearer we could add defines for the various submodes. It seems like submode may be intended to represent one of the interface modes defined by USBPHY_INTERFACE_MODE_*, but perhaps it can be repurposed for PHY_MODE_USB_HOST_SS? Thierry >=20 > Thanks, > JC >=20 > On 10/14/19 9:40 PM, Rob Herring wrote: > > On Mon, Oct 14, 2019 at 8:17 AM Thierry Reding wrote: > >> > >> 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_P= LL) > >>>> , 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 w= ith > >>>> 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 spe= ed > >>>> 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 lengt= h, > >> it doesn't really make sense to restrict the whole controller to a giv= en > >> 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. > >=20 > > Okay, but still should be common for USB PHYs IMO. > >=20 > > Rob > >=20 --4zI0WCX1RcnW9Hbu Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEiOrDCAFJzPfAjcif3SOs138+s6EFAl2oVAkACgkQ3SOs138+ s6H0XhAAkIXr/bF4284DsOZ2ZcXx5pNP+GIEKALOqU4zATVgYWQaKG8FACjwJ1vy TuKvlCN0w635625Cw+YzHot9ZsmaYdnr/m81QiLE74b94oClKSY3kftvdcmuOZMJ goQERkEraMNYL2vfhPhoUJkuEqG1k3Y2pgi/BvCuct5loRAaNCSLCtjG6H4KG5tN +36lEdTRmbtFMfc36lGdaRHb5PFe/zEXcjoJePEF56RVW9zW1/sQqIMqULYxzjh4 BAcYtJ2lJP+4/0mOJLZuqo40mVFf1p0gIPMhx0M67h9gkfNbkXb4li2+JCQ/sI9B dCF+jz3g9L3HfLtWK3AMk1Of5id5kSG3UU23+64UfmL4MWM3xYzn7D9U9bac4k7o Ua6XD7coC9Y8aRsQR+zSLkFC9/GmTQuOBlgPghQXUYHGN9dTymPIZHG7w1wPK8ik R4krezTCHLB2MjtGqoFl/A1zvHcDbqJxCbZDgq1Sk5t2ekqfy5nsu6VrxtzjgTLG p0Z7/cIyOVcj8qvb62OHS9A/zlfd2jobWRo/Hhla39cHAS4LaKWi+j9oTQ6l9z65 GeilzgAVGJiJ62oaWRI8zbXmZzaxxAOavj4WolTcL6jrmj+sfLOlqv3wh/ziXTSI E3AVNXer0JurJCQXCBz1Iwc7TPqEp+LEMEQi9hFcWrd4S1s41to= =mhb4 -----END PGP SIGNATURE----- --4zI0WCX1RcnW9Hbu--