Re: [PATCH v2 4/4] tpm: tpm_crb: Use cached tpm2_acpi_start_method

[Jarkko Sakkinen <jarkko@kernel.org>]

On Sat, Nov 14, 2026 at 07:34:34PM +0000, Siddharth Chintamaneni wrote:
> Check the cached tpm2_acpi_start_method value at the start of
> crb_acpi_probe() before mapping the ACPI TPM2 table for CRB-specific
> parameters. This avoids mapping the table when it is absent or when the
> device uses ACPI_TPM2_MEMORY_MAPPED and belongs to tpm_tis.
> 
> Signed-off-by: Siddharth Chintamaneni <sidchintamaneni@gmail.com>
> ---
>  drivers/char/tpm/tpm_crb.c | 19 ++++++++++++-------
>  1 file changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
> index 4749a9183726..c1c2b72459a2 100644
> --- a/drivers/char/tpm/tpm_crb.c
> +++ b/drivers/char/tpm/tpm_crb.c
> @@ -945,18 +945,23 @@ static int crb_acpi_probe(struct platform_device *pdev)
>  	if (!device)
>  		return -ENODEV;
>  
> -	status = acpi_get_table(ACPI_SIG_TPM2, 1,
> -				(struct acpi_table_header **) &buf);
> -	if (ACPI_FAILURE(status) || buf->header.length < sizeof(*buf)) {
> +	sm = tpm2_acpi_start_method;

sm and also priv->sm should be removed

The global should be accessed across the board when querying start
method. It should be the single source for it post-tpm_init.

> +	if (sm == ACPI_TPM2_NOT_ALLOWED) {
>  		dev_err(dev, FW_BUG "failed to get TPM2 ACPI table\n");

Drop this message.

>  		return -EINVAL;

-ENODEV


>  	}
>  
>  	/* Should the FIFO driver handle this? */
> -	sm = buf->start_method;
> -	if (sm == ACPI_TPM2_MEMORY_MAPPED) {
> -		rc = -ENODEV;
> -		goto out;
> +	if (sm == ACPI_TPM2_MEMORY_MAPPED)
> +		return -ENODEV;
> +
> +	status = acpi_get_table(ACPI_SIG_TPM2, 1,
> +				(struct acpi_table_header **)&buf);
> +	if (ACPI_FAILURE(status) || buf->header.length < sizeof(*buf)) {
> +		dev_err(dev, FW_BUG "failed to get TPM2 ACPI table\n");

Drop this message.

> +		if (ACPI_SUCCESS(status))
> +			acpi_put_table((struct acpi_table_header *)buf);
> +		return -EINVAL;

-ENODEV

>  	}
>  
>  	priv = devm_kzalloc_obj(dev, struct crb_priv);
> -- 
> 2.45.4
> 

Br, Jarkko