From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laxman Dewangan Subject: Re: [PATCH 7/7] pinctrl: tegra: Add driver to configure voltage and power state of io pads Date: Fri, 15 Apr 2016 19:29:56 +0530 Message-ID: <5710F3DC.7090906@nvidia.com> References: <1460473007-11535-1-git-send-email-ldewangan@nvidia.com> <1460473007-11535-8-git-send-email-ldewangan@nvidia.com> <5710A8A4.90309@nvidia.com> <5710BA75.2010503@nvidia.com> <5710D4E2.2030801@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Linus Walleij Cc: Stephen Warren , Thierry Reding , Alexandre Courbot , Rob Herring , Mark Rutland , Jon Hunter , "linux-tegra@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-gpio@vger.kernel.org" List-Id: linux-tegra@vger.kernel.org On Friday 15 April 2016 07:33 PM, Linus Walleij wrote: > On Fri, Apr 15, 2016 at 1:47 PM, Laxman Dewangan wrote: >> On Friday 15 April 2016 04:45 PM, Linus Walleij wrote: >>> On Fri, Apr 15, 2016 at 11:55 AM, Laxman Dewangan >>> wrote: >>> But to be sure we would like to know what is actually happening, >>> electronically speaking, when you set this up. Do you have any >>> idea? >> From electronic point of view, the value of VIL, VIH, VOL, VOH (Input/output >> voltage level for low and high state) are different when talking for 0 t >> 1.8V and 0 to 3.3V. > Yeah that I get. But since it is switched on a per-pin basis, and > this is not about what voltage is actually supplied to the I/O cell, > because that comes from the outside, it is a mystery why it is > even needed. > > I understand that there is a bit selecting driving voltage level in > the register range, what I don't understand is what that is > doing in the I/O cell. > > The bit in the register must be routed to somehing in the I/O cell > and I would like to know what. I take it that an ordinary CMOS > totem-pole push-pull output is going to work the same with 1.8 > and 3.3V alike so it's obviously not enabling any extra transistors > or anything. > > I dont have answer for this now and I need to discuss with HW team to get this info. I will be back here after discussion with HW team.