Re: question about setting TPM_CHIP_FLAG_IRQ in tpm_tis_core_init

[Jerry Snitselaar]

On Tue Nov 12 19, Jarkko Sakkinen wrote:
> On Mon, Nov 11, 2019 at 08:36:37PM -0700, Jerry Snitselaar wrote:
> > Question about 1ea32c83c699 ("tpm_tis_core: Set TPM_CHIP_FLAG_IRQ
> > before probing for interrupts").  Doesn't tpm_tis_send set this flag,
> > and setting it here in tpm_tis_core_init short circuits what
> > tpm_tis_send was doing before? There is a bug report of an interrupt
> > storm from a tpm on a t490s laptop with the Fedora 31 kernel (5.3),
> > and I'm wondering if this change could cause that. Before they got the
> > warning about interrupts not working, and using polling instead.
>
> Looks like it. Stefan?
>
> /Jarkko

Stefan is right about the condition check at the beginning of tpm_tis_send.

	if (!(chip->flags & TPM_CHIP_FLAG_IRQ) || priv->irq_tested)
		return tpm_tis_send_main(chip, buf, len);

Before his change it would've gone straight to calling
tpm_tis_send_main instead of jumping down and doing the irq test, due
to the flag not being set. With his change it should now skip this
tpm_tis_send_main call when tpm_tis_gen_interrupt is called, and then
after that time through tpm_tis_send priv->irq_tested will be set, and
the flag should be set as to whether or not irqs were working.

I should hopefully have access to a t490s in a few days so I can look at it,
and try to figure out what is happening.