linux-kernel - Re: [PATCH v5 06/10] tpm, tpm_tis: Only handle supported interrupts in wait_for_tpm

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Date:   Wed, 15 Jun 2022 21:21:34 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     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 v5 06/10] tpm, tpm_tis: Only handle supported interrupts
 in wait_for_tpm_stat()

On Fri, Jun 10, 2022 at 01:08:42PM +0200, LinoSanfilippo@....de wrote:
> From: Lino Sanfilippo <l.sanfilippo@...bus.com>
> 
> According to the TPM Interface Specification (TIS) interrupts for
> "stsValid" and "commandReady" might not be supported.
> 
> Take this into account and only wait for interrupts which are actually in
> use in wait_for_tpm_stat(). 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 | 46 ++++++++++++++++++++++++---------
>  1 file changed, 34 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 2f03fefa1706..028bec44362d 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 active_irqs = 0;

Something like sts_mask would be a better name. Calling it
'active_irqs' is a bit confusing.

> +	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->irqs_in_use & TPM_INTF_STS_VALID_INT)
> +		active_irqs |= TPM_STS_VALID;
>  
> -	if (chip->flags & TPM_CHIP_FLAG_IRQ) {
> +	if (priv->irqs_in_use & TPM_INTF_DATA_AVAIL_INT)
> +		active_irqs |= TPM_STS_DATA_AVAIL;
> +
> +	if (priv->irqs_in_use & TPM_INTF_CMD_READY_INT)
> +		active_irqs |= TPM_STS_COMMAND_READY;
> +
> +	active_irqs &= mask;
> +
> +	stop = jiffies + timeout;
> +	/* process status changes with irq support */
> +	if (active_irqs) {
> +		ret = -ETIME;
>  again:
>  		timeout = stop - jiffies;
>  		if ((long)timeout <= 0)
>  			return -ETIME;
>  		rc = wait_event_interruptible_timeout(*queue,
> -			wait_for_tpm_stat_cond(chip, mask, check_cancel,
> +			wait_for_tpm_stat_cond(chip, active_irqs, check_cancel,
>  					       &canceled),
>  			timeout);
>  		if (rc > 0) {
>  			if (canceled)
>  				return -ECANCELED;
> -			return 0;
> +			ret = 0;
>  		}
>  		if (rc == -ERESTARTSYS && freezing(current)) {
>  			clear_thread_flag(TIF_SIGPENDING);
>  			goto again;
>  		}
> -	} else {
> -		do {
> -			usleep_range(priv->timeout_min,
> -				     priv->timeout_max);
> -			status = chip->ops->status(chip);
> -			if ((status & mask) == mask)
> -				return 0;
> -		} while (time_before(jiffies, stop));
>  	}
> +
> +	if (ret)
> +		return ret;
> +
> +	mask &= ~active_irqs;
> +	if (!mask) /* all done */
> +		return 0;
> +	/* process status changes without irq support */
> +	do {
> +		status = chip->ops->status(chip);
> +		if ((status & mask) == mask)
> +			return 0;
> +		usleep_range(priv->timeout_min,
> +			     priv->timeout_max);
> +	} while (time_before(jiffies, stop));
>  	return -ETIME;
>  }
>  
> -- 
> 2.36.1
> 

BR, Jarkko