linux-kernel - Re: [PATCH v2 1/4] tpm: Use a threaded interrupt handler

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Message-ID: <YIikDCTBcMMxjots@kernel.org>
Date:   Wed, 28 Apr 2021 02:53:48 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Lino Sanfilippo <LinoSanfilippo@....de>
Cc:     peterhuewe@....de, jgg@...pe.ca, stefanb@...ux.vnet.ibm.com,
        James.Bottomley@...senpartnership.com, keescook@...omium.org,
        jsnitsel@...hat.com, ml.linux@...oe.vision,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] tpm: Use a threaded interrupt handler

On Mon, Apr 26, 2021 at 01:47:17AM +0200, Lino Sanfilippo wrote:
> Interrupt handling at least includes reading and writing the interrupt
> status register from the interrupt routine. However over SPI those accesses
> require a sleepable context, since a mutex is used in the concerning
> functions.
> For this reason request a threaded interrupt handler which is running in
> (sleepable) process context.
> 
> Signed-off-by: Lino Sanfilippo <LinoSanfilippo@....de>
> ---
>  drivers/char/tpm/tpm_tis_core.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index e7d1eab..0959559 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -781,8 +781,10 @@ static int tpm_tis_probe_irq_single(struct tpm_chip *chip, u32 intmask,
>  	int rc;
>  	u32 int_status;
>  
> -	if (devm_request_irq(chip->dev.parent, irq, tis_int_handler, flags,
> -			     dev_name(&chip->dev), chip) != 0) {
> +
> +	if (devm_request_threaded_irq(chip->dev.parent, irq, NULL,
> +				      tis_int_handler, IRQF_ONESHOT | flags,
> +				      dev_name(&chip->dev), chip) != 0) {
>  		dev_info(&chip->dev, "Unable to request irq: %d for probe\n",
>  			 irq);
>  		return -1;
> -- 
> 2.7.4
> 

Why?

https://elixir.bootlin.com/linux/v5.12/source/drivers/char/tpm/tpm_tis_core.c#L670

I don't see anything that sleeps there.

/Jarkko1