linux-kernel - Re: [tpmdd-devel] [PATCH] TPM: Issue TPM_STARTUP at driver load if the TPM has not been started

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Date:	Mon, 1 Oct 2012 11:39:08 -0600
From:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:	Kent Yoder <key@...ux.vnet.ibm.com>
Cc:	Peter.Huewe@...ineon.com, linux-kernel@...r.kernel.org,
	tpmdd-devel@...ts.sourceforge.net
Subject: Re: [tpmdd-devel] [PATCH] TPM: Issue TPM_STARTUP at driver load if
 the TPM has not been started

On Mon, Oct 01, 2012 at 12:10:03PM -0500, Kent Yoder wrote:

> > I'm not familiar enough with how the power management flow works with
> > the TPM to do this. I don't think that can be the general case
> > because:
> > 
> > 3. If stType = TPM_ST_STATE
> >   a. If the TPM has no state to restore, the TPM MUST set the internal
> >      state such that it returns TPM_FAILEDSELFTEST to all subsequent
> >      commands.
> > 
> > So you need to know a save state exists in the TPM before attempting
> > the command?
> 
>  Presumably we'd have called TPM_SaveState on suspend. It might be
> possible to set a flag based on whether we needed to call startup at
> init time that tells the driver to call save/restore state during
> suspend/resume.

Curiously the current code does call TPM_SaveState on suspend, but
relies on the BIOS to do TPM_Startup(ST_STATE) on resume, why the
asymmetry?

Anyhow, I think the thing would be something like this. I have no
means to test TPM suspend, so I'll just post this as a note here. It
will apply over v2 of my patch.

diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index b13ad77..7a8136a 100644
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -1336,10 +1336,23 @@ EXPORT_SYMBOL_GPL(tpm_pm_suspend);
 int tpm_pm_resume(struct device *dev)
 {
        struct tpm_chip *chip = dev_get_drvdata(dev);
+       struct tpm_cmd_t tpm_cmd;
 
        if (chip == NULL)
                return -ENODEV;
 
+       tpm_cmd.header.in = tpm_getcap_header;
+       tpm_cmd.params.getcap_in.cap = TPM_CAP_PROP;
+       tpm_cmd.params.getcap_in.subcap_size = cpu_to_be32(4);
+       tpm_cmd.params.getcap_in.subcap = TPM_CAP_PROP_TIS_TIMEOUT;
+       rc = transmit_cmd(chip, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE, 0);
+       if (rc == TPM_ERR_INVALID_POSTINIT) {
+               /* The BIOS did not restart the TPM, execute a startup
+                  command. */
+               dev_info(chip->dev, "Issuing TPM_STARTUP");
+               tpm_startup(chip, TPM_ST_STATE);
+       }
+
        return 0;
 }
 EXPORT_SYMBOL_GPL(tpm_pm_resume);

Jason
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