Re: [RFC v2 2/5] tpm_crb: Add new wrapper function to invoke start method

[Arun Menon <armenon@redhat.com>]

On Sat, May 09, 2026 at 05:43:10PM +0300, Jarkko Sakkinen wrote:
> On Tue, Mar 24, 2026 at 11:42:41PM +0530, Arun Menon wrote:
> > The current implementation handles different platform start methods
> > (ACPI, ARM SMC, and ARM FFA) directly within crb_send(), but it is
> > limited to triggering the CRB_START_INVOKE bit.
> > 
> > To support cmd/rsp chunking, the driver must be able to send other
> > control bits, like CRB_START_NEXT_CHUNK, using these same
> > platform-specific paths.
> > 
> > By moving this logic into a new helper function, crb_trigger_tpm(),
> > the driver can now send any required control bit across all supported
> > platforms. This prepares the driver for the upcoming chunking support.
> > 
> > No functional change is intended.
> > 
> > Signed-off-by: Arun Menon <armenon@redhat.com>
> > ---
> >  drivers/char/tpm/tpm_crb.c | 50 ++++++++++++++++++++------------------
> >  1 file changed, 27 insertions(+), 23 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
> > index 67c0061d4cab7..922bcf7a69ad5 100644
> > --- a/drivers/char/tpm/tpm_crb.c
> > +++ b/drivers/char/tpm/tpm_crb.c
> > @@ -445,6 +445,32 @@ static int tpm_crb_smc_start(struct device *dev, unsigned long func_id)
> >  }
> >  #endif
> >  
> > +static int crb_trigger_tpm(struct tpm_chip *chip, u32 start_cmd)
> 
> tpm_crb_start?

Yes, it can be renamed. On the qemu side also, its renamed and made
consistent with the spec.

> 
> I'd also split this into two commits:
> 
> 1. One that splits the helper.
> 2. Second that adds the new stuff.

Yes. Will do. Thank you.

> 
> > +{
> > +	struct crb_priv *priv = dev_get_drvdata(&chip->dev);
> > +	int rc = 0;
> > +	/* The reason for the extra quirk is that the PTT in 4th Gen Core CPUs
> > +	 * report only ACPI start but in practice seems to require both
> > +	 * CRB start, hence invoking CRB start method if hid == MSFT0101.
> > +	 */
> > +	if (priv->sm == ACPI_TPM2_COMMAND_BUFFER ||
> > +	    priv->sm == ACPI_TPM2_MEMORY_MAPPED ||
> > +	    !strcmp(priv->hid, "MSFT0101"))
> > +		iowrite32(start_cmd, &priv->regs_t->ctrl_start);
> > +	if (priv->sm == ACPI_TPM2_START_METHOD ||
> > +	    priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD)
> > +		rc = crb_do_acpi_start(chip);
> > +	if (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC) {
> > +		iowrite32(start_cmd, &priv->regs_t->ctrl_start);
> > +		rc = tpm_crb_smc_start(&chip->dev, priv->smc_func_id);
> > +	}
> > +	if (priv->sm == ACPI_TPM2_CRB_WITH_ARM_FFA) {
> > +		iowrite32(start_cmd, &priv->regs_t->ctrl_start);
> > +		rc = tpm_crb_ffa_start(CRB_FFA_START_TYPE_COMMAND, chip->locality);
> > +	}
> > +	return rc;
> > +}
> > +
> >  static int crb_send(struct tpm_chip *chip, u8 *buf, size_t bufsiz, size_t len)
> >  {
> >  	struct crb_priv *priv = dev_get_drvdata(&chip->dev);
> > @@ -470,29 +496,7 @@ static int crb_send(struct tpm_chip *chip, u8 *buf, size_t bufsiz, size_t len)
> >  	/* Make sure that cmd is populated before issuing start. */
> >  	wmb();
> >  
> > -	/* The reason for the extra quirk is that the PTT in 4th Gen Core CPUs
> > -	 * report only ACPI start but in practice seems to require both
> > -	 * CRB start, hence invoking CRB start method if hid == MSFT0101.
> > -	 */
> > -	if (priv->sm == ACPI_TPM2_COMMAND_BUFFER ||
> > -	    priv->sm == ACPI_TPM2_MEMORY_MAPPED ||
> > -	    !strcmp(priv->hid, "MSFT0101"))
> > -		iowrite32(CRB_START_INVOKE, &priv->regs_t->ctrl_start);
> > -
> > -	if (priv->sm == ACPI_TPM2_START_METHOD ||
> > -	    priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD)
> > -		rc = crb_do_acpi_start(chip);
> > -
> > -	if (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC) {
> > -		iowrite32(CRB_START_INVOKE, &priv->regs_t->ctrl_start);
> > -		rc = tpm_crb_smc_start(&chip->dev, priv->smc_func_id);
> > -	}
> > -
> > -	if (priv->sm == ACPI_TPM2_CRB_WITH_ARM_FFA) {
> > -		iowrite32(CRB_START_INVOKE, &priv->regs_t->ctrl_start);
> > -		rc = tpm_crb_ffa_start(CRB_FFA_START_TYPE_COMMAND, chip->locality);
> > -	}
> > -
> > +	rc = crb_trigger_tpm(chip, CRB_START_INVOKE);
> >  	if (rc)
> >  		return rc;
> >  
> > -- 
> > 2.53.0
> > 
> 
> BR, Jarkko
> 

Regards,
Arun Menon