linux-kernel - Re: [PATCH v4 5/6] tpm, tpm_tis: Move irq test from tpm_tis_send() to tpm_tis_probe_irq

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Date:   Wed, 11 May 2022 18:09:33 +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, lukas@...ner.de,
        p.rosenberger@...bus.com, Lino Sanfilippo <l.sanfilippo@...bus.com>
Subject: Re: [PATCH v4 5/6] tpm, tpm_tis: Move irq test from tpm_tis_send()
 to tpm_tis_probe_irq_single()

On Mon, May 09, 2022 at 10:05:58AM +0200, Lino Sanfilippo wrote:
> From: Lino Sanfilippo <l.sanfilippo@...bus.com>
> 
> There is no need to check for the irq test completion at each data
> transmission during the driver livetime. Instead do the check only once at
> driver startup.
> 
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@...bus.com>
> ---
>  drivers/char/tpm/tpm_tis_core.c | 68 +++++++++++----------------------
>  1 file changed, 22 insertions(+), 46 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index bdfde1cd71fe..4c65718feb7d 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -432,7 +432,7 @@ static void disable_interrupts(struct tpm_chip *chip)
>   * tpm.c can skip polling for the data to be available as the interrupt is
>   * waited for here
>   */
> -static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
> +static int tpm_tis_send(struct tpm_chip *chip, u8 *buf, size_t len)
>  {
>  	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
>  	int rc;
> @@ -465,30 +465,6 @@ static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
>  	return rc;
>  }
>  
> -static int tpm_tis_send(struct tpm_chip *chip, u8 *buf, size_t len)
> -{
> -	int rc, irq;
> -	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> -
> -	if (!(chip->flags & TPM_CHIP_FLAG_IRQ) ||
> -	     test_bit(TPM_TIS_IRQTEST_OK, &priv->irqtest_flags))
> -		return tpm_tis_send_main(chip, buf, len);
> -
> -	/* Verify receipt of the expected IRQ */
> -	irq = priv->irq;
> -	priv->irq = 0;
> -	chip->flags &= ~TPM_CHIP_FLAG_IRQ;
> -	rc = tpm_tis_send_main(chip, buf, len);
> -	priv->irq = irq;
> -	chip->flags |= TPM_CHIP_FLAG_IRQ;
> -	if (!test_bit(TPM_TIS_IRQTEST_OK, &priv->irqtest_flags))
> -		tpm_msleep(1);
> -	if (!test_bit(TPM_TIS_IRQTEST_OK, &priv->irqtest_flags))
> -		disable_interrupts(chip);
> -	set_bit(TPM_TIS_IRQTEST_OK, &priv->irqtest_flags);
> -	return rc;
> -}
> -
>  struct tis_vendor_durations_override {
>  	u32 did_vid;
>  	struct tpm1_version version;
> @@ -759,51 +735,54 @@ static int tpm_tis_probe_irq_single(struct tpm_chip *chip, u32 intmask,
>  
>  	rc = tpm_tis_read8(priv, TPM_INT_VECTOR(priv->locality),
>  			   &original_int_vec);
> -	if (rc < 0)
> +	if (rc < 0) {
> +		disable_interrupts(chip);
>  		return rc;
> +	}
>  
>  	rc = tpm_tis_write8(priv, TPM_INT_VECTOR(priv->locality), irq);
>  	if (rc < 0)
> -		return rc;
> +		goto out_err;
>  
>  	rc = tpm_tis_read32(priv, TPM_INT_STATUS(priv->locality), &int_status);
>  	if (rc < 0)
> -		return rc;
> +		goto out_err;
>  
>  	/* Clear all existing */
>  	rc = tpm_tis_write32(priv, TPM_INT_STATUS(priv->locality), int_status);
>  	if (rc < 0)
> -		return rc;
> +		goto out_err;
>  
>  	/* Turn on */
>  	rc = tpm_tis_write32(priv, TPM_INT_ENABLE(priv->locality),
>  			     intmask | TPM_GLOBAL_INT_ENABLE);
>  	if (rc < 0)
> -		return rc;
> +		goto out_err;
>  
>  	clear_bit(TPM_TIS_IRQTEST_OK, &priv->irqtest_flags);
> -	chip->flags |= TPM_CHIP_FLAG_IRQ;
>  
>  	/* Generate an interrupt by having the core call through to
>  	 * tpm_tis_send
>  	 */
>  	rc = tpm_tis_gen_interrupt(chip);
>  	if (rc < 0)
> -		return rc;
> +		goto out_err;
>  
> -	/* tpm_tis_send will either confirm the interrupt is working or it
> -	 * will call disable_irq which undoes all of the above.
> -	 */
> -	if (!(chip->flags & TPM_CHIP_FLAG_IRQ)) {
> -		rc = tpm_tis_write8(priv, original_int_vec,
> -				TPM_INT_VECTOR(priv->locality));
> -		if (rc < 0)
> -			return rc;
> +	tpm_msleep(1);
>  
> -		return 1;
> -	}
> +	/* Verify receipt of the expected IRQ */
> +	if (!test_bit(TPM_TIS_IRQTEST_OK, &priv->irqtest_flags))
> +		goto out_err;
> +
> +	chip->flags |= TPM_CHIP_FLAG_IRQ;
>  
>  	return 0;
> +
> +out_err:
> +	disable_interrupts(chip);
> +	tpm_tis_write8(priv, original_int_vec, TPM_INT_VECTOR(priv->locality));
> +
> +	return rc;
>  }
>  
>  /* Try to find the IRQ the TPM is using. This is for legacy x86 systems that
> @@ -1075,12 +1054,9 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>  		if (irq) {
>  			tpm_tis_probe_irq_single(chip, intmask, IRQF_SHARED,
>  						 irq);
> -			if (!(chip->flags & TPM_CHIP_FLAG_IRQ)) {
> +			if (!(chip->flags & TPM_CHIP_FLAG_IRQ))
>  				dev_err(&chip->dev, FW_BUG
>  					"TPM interrupt not working, polling instead\n");
> -
> -				disable_interrupts(chip);
> -			}
>  		} else {
>  			tpm_tis_probe_irq(chip, intmask);
>  		}
> -- 
> 2.36.0
> 

For me this looks just code shuffling.

I don't disagree but changing working code without actual semantical
reasons neither makes sense.

BR, Jarkko