From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrey Pronin Subject: Re: [PATCH v2 1/2] tpm: devicetree: document properties for cr50 Date: Wed, 27 Jul 2016 14:00:47 -0700 Message-ID: <20160727210047.GA119121@apronin> References: <1468549218-19215-1-git-send-email-apronin@chromium.org> <5274cc806888a709c639e701dad894543885b2c9.1468985673.git.apronin@chromium.org> <20160720190303.GA5620@rob-hp-laptop> <20160720194912.GA61154@apronin> <20160721210312.GA10605@rob-hp-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20160721210312.GA10605@rob-hp-laptop> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: tpmdd-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Rob Herring Cc: Mark Rutland , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Christophe Ricard , Pawel Moll , Ian Campbell , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, tpmdd-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Kumar Gala List-Id: devicetree@vger.kernel.org On Thu, Jul 21, 2016 at 04:03:12PM -0500, Rob Herring wrote: > On Wed, Jul 20, 2016 at 12:49:12PM -0700, Andrey Pronin wrote: > > On Wed, Jul 20, 2016 at 02:03:03PM -0500, Rob Herring wrote: > > > On Tue, Jul 19, 2016 at 08:41:24PM -0700, Andrey Pronin wrote: > > > > Hi Rob, > > > > > As I mentioned, there may be common properties. It doesn't seem you > > > looked, so I did: > > > > > > - spi-rx-delay-us - (optional) Microsecond delay after a read transfer. > > > - spi-tx-delay-us - (optional) Microsecond delay after a write transfer. > > > > > > Seems to me setting one or both of these should work for you. > > > > > > > Yes, good catch, my fault I didn't see those. > > But they are not exactly what I mean and need. I don't need delay after > > each read or write transfer. What is needed is a guaranteed time > > between transfers. > > > > So, if the next transaction doesn't come withing the next X ms (or us), > > we don't waste time on inserting a delays after this transaction at all. > > Following the description and always inserting a delay must work well > > for short microseconds-long delays. For longer milliseconds-long delays > > a different strategy of checking the time when the previous transaction > > was and only delaying if it was not too long ago is better. > > I'd guess that the intent is the same for all. A simple delay is > just much easier to implement. I would think implementing the more > sophisticated algorithm would work for all users. Perhaps with some > threshold for a simple delay. > > > Thus, I won't be able to re-use these properties anyways based on their > > current description in bindings/spi/spi-bus.txt. > > > > > > +- sleep-delay-ms: Time after the last SPI activity, after which the chip > > > > + may go to sleep. > > > > +- wake-start-delay-ms: Time after initiating wake up before the chip is > > > > + ready to accept commands over SPI. > > > > > > I also asked why these 2 can't be hard-coded in the driver? > > > > > > > Sorry, I just updated this patch description in v2 to indicate why they are not > > hard-coded, but didn't answer explicitly. As the firmware changes, a different > > revision of it can have a different time before it sleeps in its configuration, > > or the time it takes it to startup may be different. Thus, there's a way to > > set it here w/o changing the driver. > > The firmware and DT may not be updated in sync especially if you are > loading the firmware from the rootfs. Are you doing DT and firmware > updates without changing the kernel? > > Rob Hi Rob, Thanks for the feedback. I will hard-code those parameters in the driver instead of reading from DT. Thanks, Andrey ------------------------------------------------------------------------------