linux-kernel - Re: [PATCH v6 5/9] tpm, tpm_tis: Only handle supported interrupts

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Date:   Sun, 26 Jun 2022 09:44:02 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Lino Sanfilippo <LinoSanfilippo@....de>
Cc:     peterhuewe@....de, jgg@...pe.ca, stefanb@...ux.vnet.ibm.com,
        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 v6 5/9] tpm, tpm_tis: Only handle supported interrupts

On Sun, Jun 26, 2022 at 09:40:43AM +0300, Jarkko Sakkinen wrote:
> On Tue, Jun 21, 2022 at 03:24:43PM +0200, Lino Sanfilippo wrote:
> > From: Lino Sanfilippo <l.sanfilippo@...bus.com>
> > 
> > According to the TPM Interface Specification (TIS) support for "stsValid"
> > and "commandReady" interrupts is only optional.
> > This has to be taken into account when handling the interrupts in functions
> > like wait_for_tpm_stat(). To determine the supported interrupts use the
> > capability query.
> > 
> > Also adjust wait_for_tpm_stat() to only wait for interrupt reported status
> > changes. After that process all the remaining status changes by polling
> > the status register.
> > 
> > Signed-off-by: Lino Sanfilippo <l.sanfilippo@...bus.com>
> > ---
> >  drivers/char/tpm/tpm_tis_core.c | 119 +++++++++++++++++++-------------
> >  drivers/char/tpm/tpm_tis_core.h |   1 +
> >  2 files changed, 72 insertions(+), 48 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> > index 09d8f04cbc81..cb469591373a 100644
> > --- a/drivers/char/tpm/tpm_tis_core.c
> > +++ b/drivers/char/tpm/tpm_tis_core.c
> > @@ -53,41 +53,63 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
> >  	long rc;
> >  	u8 status;
> >  	bool canceled = false;
> > +	u8 sts_mask = 0;
> > +	int ret = 0;
> >  
> >  	/* check current status */
> >  	status = chip->ops->status(chip);
> >  	if ((status & mask) == mask)
> >  		return 0;
> >  
> > -	stop = jiffies + timeout;
> > +	/* check what status changes can be handled by irqs */
> > +	if (priv->int_mask & TPM_INTF_STS_VALID_INT)
> > +		sts_mask |= TPM_STS_VALID;
> >  
> > -	if (chip->flags & TPM_CHIP_FLAG_IRQ) {
> > +	if (priv->int_mask & TPM_INTF_DATA_AVAIL_INT)
> > +		sts_mask |= TPM_STS_DATA_AVAIL;
> > +
> > +	if (priv->int_mask & TPM_INTF_CMD_READY_INT)
> > +		sts_mask |= TPM_STS_COMMAND_READY;
> > +
> > +	sts_mask &= mask;
> 
> I would instead mask out bits and write a helper function
> taking care of this:
> 
> static u8 tpm_tis_filter_sts_mask(u8 int_mask, u8 sts_mask)
> {
>         struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);

Ignore this line (wrote this out of top of my head).

>         if (!(int_mask & TPM_INTF_STS_VALID_INT))
>                 sts_mask &= ~TPM_STS_VALID;
> 
>         if (!(int_mask & TPM_INTF_DATA_AVAIL_INT))
>                 sts_mask &= ~TPM_STS_DATA_AVAIL;
> 
>         if (!(int_mask & TPM_INTF_CMD_READY_INT))
> 		sts_mask &= ~TPM_STS_COMMAND_READY;
> 
>         return sts_mask;
> }
> 
> Less operations and imho somewhat cleaner structure.
> 
> Add suggested-by if you want.
> 
> BR, Jarkko