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

[Arun Menon <armenon@redhat.com>]

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)
+{
+	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