linux-kernel - Re: [RFC PATCH v5] tpm_tis: verify interrupt during init

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Message-ID: <20140902172015.GD13956@obsidianresearch.com>
Date:	Tue, 2 Sep 2014 11:20:15 -0600
From:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:	Scot Doyle <lkml14@...tdoyle.com>
Cc:	Peter Huewe <peterhuewe@....de>, Ashley Lai <ashley@...leylai.com>,
	Marcel Selhorst <tpmdd@...horst.net>,
	Stefan Berger <stefanb@...ux.vnet.ibm.com>,
	Luigi Semenzato <semenzato@...gle.com>,
	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v5] tpm_tis: verify interrupt during init

On Sat, Aug 30, 2014 at 11:23:56PM +0000, Scot Doyle wrote:
> On Sat, 30 Aug 2014, Jason Gunthorpe wrote:
> 
> > On Fri, Aug 29, 2014 at 11:59:32PM +0000, Scot Doyle wrote:
> >
> >> I tried calling tpm_get_timeouts only during the interrupt test, but again
> >> was timed out after 30 seconds. The interrupt wait in tis_send calls
> >> tpm_calc_ordinal_duration, which uses a default timeout of two minutes
> >> when chip->vendor.duration[duration_idx] hasn't been set. Thus the second
> >> call to tpm_get_timeouts in tpm_tis_init.
> >
> > So the strategy is to read the timeouts and hope that the chip reports
> > something small and reasonable, then do a second read?
> >
> > Seems reasonable, but with this new arrangement we could also use an
> > alternate polling logic for 'testing_int' that did the normal polling
> > loop unconditionally and then checked if the interrupt was
> > delivered. This would give a minimal dealy.
> 
> I like the idea. And then tpm_do_selftest could be used for the interrupt 
> verification instead of a second tpm_get_timeouts?

Yes, or the first tpm_get_timeouts can be used - Long term I would
like to see the entire tpm_get_timeouts,self_test,startup, etc
sequence moved into core code, so I don't really want to see drivers
splitting the sequence up.

Ideally the driver will just automatically test the IRQ on the very
first command it executes. That is now a very small easy step, so lets
just do that..

> The output is now
> [    1.526798] tpm_tis 00:08: 1.2 TPM (device-id 0xB, rev-id 16)
> [    5.914732] tpm_tis 00:08: [Firmware Bug]: TPM interrupt not working, polling instead

Cool, why did it take 4 seconds though?
 
> +struct priv_data {
> +	int test_irq;

Probably don't need this...

> @@ -358,13 +379,27 @@ static int tpm_tis_send(struct tpm_chip *chip, u8 *buf, size_t len)
>

And this can probably just become:

bool test_irq = priv->int_count == 0;
int oldirq = chip->vendor.irq;

> +	((struct priv_data*)chip->vendor.priv)->int_count++;

.. Seems like there was no need for it to count, this can just be =
true?

> -	if (tpm_do_selftest(chip)) {
> -		dev_err(dev, "TPM self test failed\n");
> -		rc = -ENODEV;
> -		goto out_err;
> -	}

And move tpm_get_timeouts down too.. Keep the sequence together.

Looks really good to me, I can try and test the next version here this
week.

Jason
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