From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Ruppert Subject: Re: [PATCH 1/2] i2c-designware: make *CNT values configurable Date: Mon, 12 Aug 2013 09:48:00 +0200 Message-ID: <20130812074800.GA23792@ab42.lan> References: <20130711101330.GP4898@intel.com> <51DFB6C1.4040001@pobox.com> <20130712085140.GY4898@intel.com> <51E0E76B.1040304@pobox.com> <20130716111616.GA25835@ab42.lan> <51E6ACBE.7000509@pobox.com> <20130722131706.GA24081@ab42.lan> <51EFE550.1000507@pobox.com> <20130805093126.GE20936@ab42.lan> <20130805100225.GA9694@katana> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="HlL+5n6rz5pIUxbD" Return-path: Content-Disposition: inline In-Reply-To: <20130805100225.GA9694@katana> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Wolfram Sang Cc: Shinya Kuribayashi , mika.westerberg-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-i2c@vger.kernel.org --HlL+5n6rz5pIUxbD Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Aug 05, 2013 at 12:02:26PM +0200, Wolfram Sang wrote: >=20 > > > >Would it make sense to add generic I2C device tree properties for th= ose > > > >parameters? These parameters are independent of the actual bus drive= r, > > > >rather a PCB property... And as such the correct place would be devi= ce > > > >tree or ACPI or similar. > > >=20 > > > If there are other bus drivers that make use of tr/tf transition > > > times, I think it makes sense. > >=20 > > Wolfram, what's your opinion on this? >=20 > If it is a PCB property, it makes sense to have generic bindings for > it. Can they have very-safe defaults and thus be optional? We can definitely have safe defaults that work for a given driver/hardware. I don't think the same defaults would be safe for all drivers/hardware: The timing strategies of different I2C hardware seems to vary widely (which edges of the clock are sampled, how does different hardware deal with hold times etc) and depending on which parameters are available to the driver to control these timings, the safe values would either have to be the minimum or the maximum in the range allowed by the I2C specification. Every driver would thus have to implement its own defaults in case the properties are not defined. Christian --HlL+5n6rz5pIUxbD Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.14 (GNU/Linux) iEYEARECAAYFAlIIkzAACgkQbI8SbDT4m4/F5gCgqWnchQJiBmeIDuhHZ8TL6RPB K0QAnjR/hDxVcDa3oJ95d1XkmSk4SHpC =kkYe -----END PGP SIGNATURE----- --HlL+5n6rz5pIUxbD--