linux-kernel - Re: [tpmdd-devel] [PATCH] tpm, tpm_crb: Handle 64-bit resource in crb_check

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Date:   Tue, 3 Jan 2017 19:11:49 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Jiandi An <anjiandi@...eaurora.org>
Cc:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [tpmdd-devel] [PATCH] tpm, tpm_crb: Handle 64-bit resource in
 crb_check_resource()

On Tue, Dec 20, 2016 at 12:19:27AM -0600, Jiandi An wrote:
> The control area buffer is specified in the TPM2.0 static ACPI table.  TPM
> CRB driver maps the control area address and reads out cmd and rsp buffer
> addresses and maps them.  There is no requirement in the TCG TPM ACPI spec
> for specifying _CRS to describe the control area buffer.  When I rebased
> the early prototype for CRB driver ARM64 enablement to the latest kernel,
> I hit this issue where I have to specify _CRS method.  So in _CRS method
> I specify the same control area address that's in the TPM2.0 static ACPI table.
> 
> I see the _CRS requirement in the CRB driver is for resource synchronization
> between the TIS and CRB drivers to support force mode in TIS. Could I get some
> background on that so I could be more careful not breaking TIS while making
> changes to CRB driver for ARM64 enablement?

At least couple of reasons:

- _CRS is required to access locality registers (check my patch set
  that is waiting for review/testing).
- On x86 and PTT _CRS always exists and that's the only platform
  where this driver has been used so far.

/Jarkko