Re: [PATCH v3 3/4] tpm: tpm_tis: Use cached tpm2_acpi_start_method

[Jarkko Sakkinen <jarkko@kernel.org>]

On Sun, Nov 15, 2026 at 01:34:55AM +0000, Siddharth Chintamaneni wrote:
> Use the cached tpm2_acpi_start_method value instead of mapping and
> unmapping the ACPI TPM2 table again during probe. Remove
> check_acpi_tpm2() and open-code the start method check directly in
> tpm_tis_init(), returning -ENODEV when the device does not use
> ACPI_TPM2_MEMORY_MAPPED.
> 
> Signed-off-by: Siddharth Chintamaneni <sidchintamaneni@gmail.com>
> ---
>  drivers/char/tpm/tpm_tis.c | 45 +++++---------------------------------
>  1 file changed, 6 insertions(+), 39 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis.c b/drivers/char/tpm/tpm_tis.c
> index 6f8344894ea5..df2d8c1c2be0 100644
> --- a/drivers/char/tpm/tpm_tis.c
> +++ b/drivers/char/tpm/tpm_tis.c
> @@ -127,45 +127,11 @@ static inline int is_itpm(struct acpi_device *dev)
>  #endif
>  
>  #if defined(CONFIG_ACPI)
> -#define DEVICE_IS_TPM2 1
> -
>  static const struct acpi_device_id tpm_acpi_tbl[] = {
> -	{"MSFT0101", DEVICE_IS_TPM2},
> +	{"MSFT0101"},
>  	{},
>  };
>  MODULE_DEVICE_TABLE(acpi, tpm_acpi_tbl);
> -
> -static int check_acpi_tpm2(struct device *dev)
> -{
> -	const struct acpi_device_id *aid = acpi_match_device(tpm_acpi_tbl, dev);
> -	struct acpi_table_tpm2 *tbl;
> -	acpi_status st;
> -	int ret = 0;
> -
> -	if (!aid || aid->driver_data != DEVICE_IS_TPM2)
> -		return 0;


Jason, can you remind me what was the deal with this flag?

> -
> -	/* If the ACPI TPM2 signature is matched then a global ACPI_SIG_TPM2
> -	 * table is mandatory
> -	 */
> -	st = acpi_get_table(ACPI_SIG_TPM2, 1, (struct acpi_table_header **)&tbl);
> -	if (ACPI_FAILURE(st) || tbl->header.length < sizeof(*tbl)) {
> -		dev_err(dev, FW_BUG "failed to get TPM2 ACPI table\n");
> -		return -EINVAL;
> -	}
> -
> -	/* The tpm2_crb driver handles this device */
> -	if (tbl->start_method != ACPI_TPM2_MEMORY_MAPPED)
> -		ret = -ENODEV;
> -
> -	acpi_put_table((struct acpi_table_header *)tbl);
> -	return ret;
> -}
> -#else
> -static int check_acpi_tpm2(struct device *dev)
> -{
> -	return 0;
> -}
>  #endif
>  
>  static int tpm_tcg_read_bytes(struct tpm_tis_data *data, u32 addr, u16 len,
> @@ -222,11 +188,12 @@ static int tpm_tis_init(struct device *dev, struct tpm_info *tpm_info)
>  {
>  	struct tpm_tis_tcg_phy *phy;
>  	int irq = -1;
> -	int rc;
>  
> -	rc = check_acpi_tpm2(dev);
> -	if (rc)
> -		return rc;
> +#ifdef CONFIG_ACPI
> +	if (acpi_match_device(tpm_acpi_tbl, dev) &&
> +	    tpm2_acpi_start_method != ACPI_TPM2_MEMORY_MAPPED)
> +		return -ENODEV;
> +#endif
>  
>  	phy = devm_kzalloc_obj(dev, struct tpm_tis_tcg_phy);
>  	if (phy == NULL)
> -- 
> 2.45.4
> 

Br, Jarkko