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From: Andrey Pronin <apronin@chromium.org>
To: Rob Herring <robh@kernel.org>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
	Peter Huewe <peterhuewe@gmx.de>,
	Marcel Selhorst <tpmdd@selhorst.net>,
	Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
	tpmdd-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org,
	Christophe Ricard <christophe.ricard@gmail.com>,
	Pawel Moll <pawel.moll@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Ian Campbell <ijc+devicetree@hellion.org.uk>,
	Kumar Gala <galak@codeaurora.org>,
	devicetree@vger.kernel.org
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> (raw)
In-Reply-To: <20160721210312.GA10605@rob-hp-laptop>

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

  reply index

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-15  2:20 [PATCH 0/2] tpm: add driver for cr50 on SPI Andrey Pronin
2016-07-15  2:20 ` [PATCH 1/2] tpm: devicetree: document properties for cr50 Andrey Pronin
2016-07-15  4:05   ` Guenter Roeck
2016-07-15 17:31     ` Andrey Pronin
2016-07-15 18:28       ` Guenter Roeck
2016-07-17 13:28   ` Rob Herring
2016-07-15  2:20 ` [PATCH 2/2] tpm: add driver for cr50 on SPI Andrey Pronin
2016-07-15  3:32   ` Jason Gunthorpe
2016-07-15  3:44     ` Andrey Pronin
2016-07-19 12:55       ` Jarkko Sakkinen
2016-07-20  0:24         ` Andrey Pronin
2016-07-20 17:03           ` Jason Gunthorpe
2016-07-21 18:10             ` Andrey Pronin
2016-07-21 21:00               ` Jason Gunthorpe
2016-07-15  2:28 ` [PATCH 0/2] " Peter Huewe
2016-07-15  2:50   ` Andrey Pronin
2016-07-15  3:28     ` Jason Gunthorpe
2016-07-15 17:15       ` Andrey Pronin
2016-07-19 12:56 ` Jarkko Sakkinen
2016-07-20  3:41 ` [PATCH v2 " Andrey Pronin
2016-07-20  3:41   ` [PATCH v2 1/2] tpm: devicetree: document properties for cr50 Andrey Pronin
2016-07-20 19:03     ` Rob Herring
2016-07-20 19:49       ` Andrey Pronin
2016-07-20 19:54         ` Jason Gunthorpe
2016-07-27 21:02           ` Andrey Pronin
2016-07-21 21:03         ` Rob Herring
2016-07-27 21:00           ` Andrey Pronin [this message]
2016-07-20  3:41   ` [PATCH v2 2/2] tpm: add driver for cr50 on SPI Andrey Pronin
2016-07-25 17:09   ` Aw: [PATCH v2 0/2] " Peter Huewe
2016-07-27 21:12     ` Andrey Pronin
2016-07-28  4:25 ` [PATCH v3 " Andrey Pronin
2016-07-28  4:25   ` [PATCH v3 1/2] tpm: devicetree: document properties for cr50 Andrey Pronin
2016-07-28  4:25   ` [PATCH v3 2/2] tpm: add driver for cr50 on SPI Andrey Pronin
2016-07-28 23:01     ` Dmitry Torokhov
2016-07-28 23:17       ` Jason Gunthorpe
2016-07-29  3:01         ` Andrey Pronin
2016-07-29  1:55 ` [PATCH v4 0/2] " Andrey Pronin
2016-07-29  1:55   ` [PATCH v4 1/2] tpm: devicetree: document properties for cr50 Andrey Pronin
2016-07-29 17:27     ` Jason Gunthorpe
2016-07-29 21:42       ` Rob Herring
2016-08-09 10:08     ` Jarkko Sakkinen
2016-07-29  1:55   ` [PATCH v4 2/2] tpm: add driver for cr50 on SPI Andrey Pronin
2016-08-09 10:20     ` Jarkko Sakkinen

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