Date: Wed, 1 Mar 2017 11:43:33 -0700
From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        linux-kernel@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
        tpmdd-devel@lists.sourceforge.net, Sonny Rao <sonnyrao@chromium.org>
Subject: Re: [tpmdd-devel] [PATCH] tpm: do not suspend/resume if power stays
 on
Message-ID: <20170301184333.GA12197@obsidianresearch.com>
References: <20170301115116.19696-1-enric.balletbo@collabora.com>
 <20170301135429.GF28874@leverpostej>
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> > +Optional properties:
> > +- powered-while-suspended: present when the TPM is left powered on between
> > +  suspend and resume (makes the suspend/resume callbacks do nothing).
> 
> This reads like configuration rather than a HW property.

I read this to mean the HW does not cut power to the TPM when Linux
does 'suspend'.

We recently added global suspend/resume callbacks to the TPM
core. Those call backs do not power off the TPM, they just prepare its
internal state to loose power to the chip. Skipping that process on
hardware that does not power-off the TPM makes sense to me.

But, Sonny, perhaps this should be a global flag in tpm_chip, not a
per-interface-driver override?

Jason