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

Lino Sanfilippo
2023-05-26T00:37:42Z

On 24.05.23 17:30, Jarkko Sakkinen wrote:
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>
> On Wed May 24, 2023 at 6:58 AM EEST, Jarkko Sakkinen wrote:
>>> rc = tpm_tis_read32(priv, TPM_INT_STATUS(priv->locality), &interrupt);
>>> if (rc < 0)
>>> - return IRQ_NONE;
>>> + goto unhandled;
>>>
>>> if (interrupt == 0)
>>> - return IRQ_NONE;
>>> + goto unhandled;
>>>
>>> set_bit(TPM_TIS_IRQ_TESTED, &priv->flags);
>>> if (interrupt & TPM_INTF_DATA_AVAIL_INT)
>>> @@ -780,10 +829,14 @@ static irqreturn_t tis_int_handler(int dummy, void *dev_id)
>>> 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;
>>>
>>> tpm_tis_read32(priv, TPM_INT_STATUS(priv->locality), &interrupt);
>>> return IRQ_HANDLED;
>>> +
>>> +unhandled:
>>> + tpm_tis_process_unhandled_interrupt(chip);
>>> + return IRQ_HANDLED;
>>> }
>
> Some minor glitches I noticed.
>
> You could simplify the flow by making the helper to return IRQ_NONE.
>
> E.g.
>
> tpm_tis_relinquish_locality(chip, 0);
> if (rc < 0)
> return tpm_tis_process_unhandled_interrupt(chip);

Agreed, this way we could spare a few lines in the interrupt handler (but note
that the implementation only returns IRQ_HANDLED never IRQ_NONE. This is to prevent
the generic irq code from doing its own interrupt storm handling before the TPM driver
had a chance to fall back to polling).

>
> I'd recommend changing the function name simply tpm_tis_rollback_interrupt().

> Also tpm_tis_handle_irq_storm() is a pretty bad function name
> because handle also can mean anything. You are resetting to the
> polling mode, right?
>
> So perhaps that could be e.g. tpm_tis_reenable_polling? I'm open
> for any other name but it really needs to give a hint what the
> function does.

tpm_tis_reenable_polling() sounds good to me.

Regards,
Lino