Re: question about setting TPM_CHIP_FLAG_IRQ in tpm_tis_core_init

[Stefan Berger]

On 11/12/19 9:24 AM, Jerry Snitselaar wrote:
> On Tue Nov 12 19, Stefan Berger wrote:
> > On 11/11/19 10:36 PM, 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.
> > I set this flag for the TIS because it wasn't set anywhere else. 
> > tpm_tis_send() wouldn't set the flag but go via the path:
> >
> > if (!(chip->flags & TPM_CHIP_FLAG_IRQ) || priv->irq_tested)
> >
> >         return tpm_tis_send_main(chip, buf, len);
> >
> > the only other line for the TIS to set the IRQ flag was in the same 
> > function further below, though that wouldn't be reached due to the 
> > above:
> >
> > [...]
> >
> > priv->irq = irq;
> >
> > chip->flags |= TPM_CHIP_FLAG_IRQ;
> >
> >
> >    Stefan
>
> Ugh, you're right I was reading that as ! around both the flag and 
> priv->irq_tested.
>
> Should the flag be cleared if tpm_tis_probe_irq_single fails prior to 
> calling
> tpm_tis_gen_interrupt?
The disable_interrupts() should be called to reset the flag if, while 
probing, the interrupt handler wasn't called. Maybe that t490s returns 
either via this path

https://elixir.bootlin.com/linux/latest/source/drivers/char/tpm/tpm_tis_core.c#L631

or this one here

https://elixir.bootlin.com/linux/latest/source/drivers/char/tpm/tpm_tis_core.c#L634

thinking the (shared) interrupt is not for it?! But this would mean 
TPM_INT_STATUS is broken...