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 14:01:28 +0200 Message-ID: <20191017120128.GE3122066@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="HeFlAV5LIbMFYYuh" 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 , Rob Herring Cc: 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 --HeFlAV5LIbMFYYuh 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. > 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"); Regarding this, I'm not sure how Rob imagined the generic properties to work. Perhaps he was thinking about something like the max-link-speed property found in the PCI bindings. We could have something like this: - max-link-speed: If present this property specifies the USB generation supported on the PHY/port. Must be: 1: for USB 3.1 Gen 1 (a.k.a. USB 3.0) 2: for USB 3.1 Gen 2 I'm not sure if we need to consider anything prior to USB 3.0. I suppose we could do a similar mapping to what I proposed for the PHY ->set_mode callback: - max-link-speed: If present this property specifies the USB generation supported on the PHY/port. Must be: 0x0100: for USB 1.0 (Low-Speed) 0x0101: for USB 1.1 (Full-Speed) 0x0200: for USB 2.0 (Hi-Speed) 0x0300: for USB 3.0 (SuperSpeed) (a.k.a. USB 3.1 Gen 1) 0x0301: for USB 3.1 (SuperSpeed 10 Gbit/s) (a.k.a. USB 3.1 Gen 2) 0x0302: for USB 3.2 (SuperSpeed 20 Gbit/s) (a.k.a. USB 3.2 Gen 2 x = 2) ... Or those could just be sequentially enumerated, like in the above example. Rob, any thoughts? Thierry > 3. In individual phy driver, to add SOC/PHY specific programming accordin= gly. >=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 --HeFlAV5LIbMFYYuh Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEiOrDCAFJzPfAjcif3SOs138+s6EFAl2oWBUACgkQ3SOs138+ s6H6Lg//Z16LUbdt8qinrY+mOKkJzVJyY9gk+oxK+7eqnRev93F97H/5xmv+XL4y WL5gKVxkEzbuca0zrpU/nK0xxNRVQhCXQkCv7ao2dc4M16ZxUUKG6Hskgv1Pa4Ll nHcmxN6lNmnCH+RVmYM+AoojBUAmaxbga1atV96DBY/6lqxUl3CtkHNFzSyfGw1S TQ5er1i1HpEuHOqY1Fsx2XTo0x3akWJgtPL/wvnw/exNN+tPXOdgXqJXvU3LF8S1 3bFVF/o23jN6FBnVtzTsaLR5lZyOc5HhvDiwtOUWptck0wmWmeOiL4G5QGj0Cks4 pN5BVm7Of69i5YLWWJWM6VWX8Mo27l+/u/fUkqvyp5QpTpGdrArVbOWhZg+iqpsH gSeU7Uhw6xdvTrgqnH+5wKH6vdb82W19SQ+xeu01mEiMHsUp0CneAxoafQrH5DIy TKDfegIEfEGzEbDNYUn1k7ZMjF+5tO1JCOQ6ExLpIknbShWJG7cCi0w0qpeni83F 73H7Sk/32VjO4TJDUe6PbdEBrmGDWHDU3S6cZpgOTujd+tbD+1TNTL3rA40pRXoo 8ikBMJlfKDlnKjhdCtIrtT+OgOlSeA6poK73FfK/I2pvqZuCGNoGuubsvyel1xoK 3egGGoIm5LMurdn4oazcaMcPJt2/YABalS1AYgoJ+6Y+y+oKWnw= =wH+F -----END PGP SIGNATURE----- --HeFlAV5LIbMFYYuh--