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

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Message-Id: <CSUM65JDEX5D.8GL20PUI2XDV@suppilovahvero>
Date:   Wed, 24 May 2023 18:30:27 +0300
From:   "Jarkko Sakkinen" <jarkko@...nel.org>
To:     "Jarkko Sakkinen" <jarkko@...nel.org>,
        "Lino Sanfilippo" <LinoSanfilippo@....de>, <peterhuewe@....de>,
        <jgg@...pe.ca>
Cc:     <jsnitsel@...hat.com>, <hdegoede@...hat.com>,
        <oe-lkp@...ts.linux.dev>, <lkp@...el.com>,
        <peter.ujfalusi@...ux.intel.com>, <peterz@...radead.org>,
        <linux@...ewoehner.de>, <linux-integrity@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <l.sanfilippo@...bus.com>,
        <lukas@...ner.de>, <p.rosenberger@...bus.com>
Subject: Re: [PATCH 1/2] tpm, tpm_tis: Handle interrupt storm

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);

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.

BR, Jarkko