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, 20 Jul 2016 12:49:12 -0700 [thread overview]
Message-ID: <20160720194912.GA61154@apronin> (raw)
In-Reply-To: <20160720190303.GA5620@rob-hp-laptop>
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.
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.
Andrey
next prev parent reply other threads:[~2016-07-20 19:49 UTC|newest]
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 [this message]
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
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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