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Subject: Re: [PATCH] tpm_tis: Disable interrupts on ThinkPad T490s
To:     Jerry Snitselaar <jsnitsel@redhat.com>,
        linux-integrity@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, jarkko@kernel.org,
        Peter Huewe <peterhuewe@gmx.de>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        James Bottomley <James.Bottomley@HansenPartnership.com>
References: <20201015214430.17937-1-jsnitsel@redhat.com>
From:   Hans de Goede <hdegoede@redhat.com>
Message-ID: <cb153887-1044-0b48-c65a-b6257c5b91f2@redhat.com>
Date:   Fri, 16 Oct 2020 08:10:19 +0200
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Hi,

On 10/15/20 11:44 PM, Jerry Snitselaar wrote:
> There is a misconfiguration in the bios of the gpio pin used for the
> interrupt in the T490s. When interrupts are enabled in the tpm_tis
> driver code this results in an interrupt storm. This was initially
> reported when we attempted to enable the interrupt code in the tpm_tis
> driver, which previously wasn't setting a flag to enable it. Due to
> the reports of the interrupt storm that code was reverted and we went back
> to polling instead of using interrupts. Now that we know the T490s problem
> is a firmware issue, add code to check if the system is a T490s and
> disable interrupts if that is the case. This will allow us to enable
> interrupts for everyone else. If the user has a fixed bios they can
> force the enabling of interrupts with tpm_tis.interrupts=1 on the
> kernel command line.
> 
> Cc: jarkko@kernel.org
> Cc: Peter Huewe <peterhuewe@gmx.de>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Reviewed-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> Signed-off-by: Jerry Snitselaar <jsnitsel@redhat.com>

Patch looks good to me:

Reviewed-by: Hans de Goede <hdegoede@redhat.com>

Regards,

Hans


> ---
>   drivers/char/tpm/tpm_tis.c | 29 +++++++++++++++++++++++++++--
>   1 file changed, 27 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis.c b/drivers/char/tpm/tpm_tis.c
> index 0b214963539d..4ed6e660273a 100644
> --- a/drivers/char/tpm/tpm_tis.c
> +++ b/drivers/char/tpm/tpm_tis.c
> @@ -27,6 +27,7 @@
>   #include <linux/of.h>
>   #include <linux/of_device.h>
>   #include <linux/kernel.h>
> +#include <linux/dmi.h>
>   #include "tpm.h"
>   #include "tpm_tis_core.h"
>   
> @@ -49,8 +50,8 @@ static inline struct tpm_tis_tcg_phy *to_tpm_tis_tcg_phy(struct tpm_tis_data *da
>   	return container_of(data, struct tpm_tis_tcg_phy, priv);
>   }
>   
> -static bool interrupts = true;
> -module_param(interrupts, bool, 0444);
> +static int interrupts = -1;
> +module_param(interrupts, int, 0444);
>   MODULE_PARM_DESC(interrupts, "Enable interrupts");
>   
>   static bool itpm;
> @@ -63,6 +64,28 @@ module_param(force, bool, 0444);
>   MODULE_PARM_DESC(force, "Force device probe rather than using ACPI entry");
>   #endif
>   
> +static int tpm_tis_disable_irq(const struct dmi_system_id *d)
> +{
> +	if (interrupts == -1) {
> +		pr_notice("tpm_tis: %s detected: disabling interrupts.\n", d->ident);
> +		interrupts = 0;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct dmi_system_id tpm_tis_dmi_table[] = {
> +	{
> +		.callback = tpm_tis_disable_irq,
> +		.ident = "ThinkPad T490s",
> +		.matches = {
> +			DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
> +			DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T490s"),
> +		},
> +	},
> +	{}
> +};
> +
>   #if defined(CONFIG_PNP) && defined(CONFIG_ACPI)
>   static int has_hid(struct acpi_device *dev, const char *hid)
>   {
> @@ -192,6 +215,8 @@ static int tpm_tis_init(struct device *dev, struct tpm_info *tpm_info)
>   	int irq = -1;
>   	int rc;
>   
> +	dmi_check_system(tpm_tis_dmi_table);
> +
>   	rc = check_acpi_tpm2(dev);
>   	if (rc)
>   		return rc;
>