linux-kernel - Re: [PATCH] tpm_tis: Add missing start/stop_tpm

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Date:   Mon, 25 Jan 2021 09:18:46 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Lukasz Majczak <lma@...ihalf.com>
Cc:     Peter Huewe <peterhuewe@....de>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        Radoslaw Biernacki <rad@...ihalf.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Alex Levin <levinale@...gle.com>
Subject: Re: [PATCH] tpm_tis: Add missing start/stop_tpm_chip calls

Hi Lukasz,

On Sat, Jan 23, 2021 at 02:42:47AM +0100, Lukasz Majczak wrote:
> There is a missing call to start_tpm_chip before the call to
> the tpm_get_timeouts() and tpm_tis_probe_irq_single(). As the current
> approach maight work for tpm2, it fails for tpm1.x - in that case
> call to tpm_get_timeouts() or tpm_tis_probe_irq_single() tries to
> transmit TPM commands on a disabled chip what what doesn't succeed

s/what what/what/

> and in turn causes tpm_tis_core_init() to fail.
> Tested on Samsung Chromebook Pro (Caroline).
> 
> Signed-off-by: Lukasz Majczak <lma@...ihalf.com>
> ---
>  drivers/char/tpm/tpm_tis_core.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 92c51c6cfd1b..ff0e5fe46a9d 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -1063,12 +1063,16 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>  	init_waitqueue_head(&priv->read_queue);
>  	init_waitqueue_head(&priv->int_queue);
>  	if (irq != -1) {
> +		rc = tpm_chip_start(chip);

Unless I am missing something, the underlying problem seems to be
the calls to tpm1_getcap(). From other code calling this function,
it looks like it may only require tpm_clk_enable() to work.

With that in mind, would it possibly be better to call tpm_clk_enable()
and tpm_clk_disable() around the calls to tpm1_getcap(), ie in
tpm1_get_timeouts() and in tpm_tis_gen_interrupt() ?

This would avoid the unnecessary calls to tpm_chip_start() and
tpm_chip_stop() for tpm2 chips.

Thanks,
Guenter


> +		if (rc)
> +			goto out_err;
>  		/* Before doing irq testing issue a command to the TPM in polling mode
>  		 * to make sure it works. May as well use that command to set the
>  		 * proper timeouts for the driver.
>  		 */
>  		if (tpm_get_timeouts(chip)) {
>  			dev_err(dev, "Could not get TPM timeouts and durations\n");
> +			tpm_chip_stop(chip);
>  			rc = -ENODEV;
>  			goto out_err;
>  		}
> @@ -1085,6 +1089,7 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>  		} else {
>  			tpm_tis_probe_irq(chip, intmask);
>  		}
> +		tpm_chip_stop(chip);
>  	}
>  
>  	rc = tpm_chip_register(chip);