Re: [PATCH 1/2] tpm, tpm_tis: Handle interrupt storm

Lukas Wunner
2023-05-23T07:56:55Z

On Tue, May 23, 2023 at 09:48:23AM +0300, Péter Ujfalusi wrote:
> On 22/05/2023 17:31, Lino Sanfilippo wrote:
[...]
> This looked promising, however it looks like the UPX-i11 needs the DMI
> quirk.

Why is that? Is there a fundamental problem with the patch or is it
a specific issue with that device?

> > --- a/drivers/char/tpm/tpm_tis_core.c
> > +++ b/drivers/char/tpm/tpm_tis_core.c
> > @@ -752,6 +752,55 @@ static bool tpm_tis_req_canceled(struct tpm_chip *chip, u8 status)
> > return status == TPM_STS_COMMAND_READY;
> > }
> >
> > +static void tpm_tis_handle_irq_storm(struct tpm_chip *chip)
> > +{
> > + struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> > + int intmask = 0;
> > +
> > + dev_err(&chip->dev, HW_ERR
> > + "TPM interrupt storm detected, polling instead\n");
>
> Should this be dev_warn or even dev_info level?

The corresponding message emitted in tpm_tis_core_init() for
an interrupt that's *never* asserted uses dev_err(), so using
dev_err() here as well serves consistency:

dev_err(&chip->dev, FW_BUG
"TPM interrupt not working, polling instead\n");

That way the same severity is used both for the never asserted and
the never deasserted interrupt case.

> > + if (priv->unhandled_irqs > MAX_UNHANDLED_IRQS)
> > + tpm_tis_handle_irq_storm(chip);
>
> Will the kernel step in and disbale the IRQ before we would have
> detected the storm?

No. The detection of spurious interrupts in note_interrupt()
hinges on handlers returning IRQ_NONE. And this patch makes
tis_int_handler() always return IRQ_HANDLED, thus pretending
success to genirq code.

> > rc = tpm_tis_write32(priv, TPM_INT_STATUS(priv->locality), interrupt);
> > tpm_tis_relinquish_locality(chip, 0);
> > if (rc < 0)
> > - return IRQ_NONE;
> > + goto unhandled;
>
> This is more like an error than just unhandled IRQ. Yes, it was ignored,
> probably because it is common?

The interrupt may be shared and then it's not an error.

Thanks,

Lukas