[SeaBIOS] [PATCH 1/3] tpm: Wait for tpmRegValidSts flags on CRQ interface before probing

[Stefan Berger]

Wait for the tpmRegValidSts flag on the TPM_LOC_STATE_x register.

Since it's not quite clear when this flag may become valid, we request
access to the interace on locality 0, which must then make it valid.

Signed-off-by: Stefan Berger 
---
 src/hw/tpm_drivers.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/hw/tpm_drivers.c b/src/hw/tpm_drivers.c
index ed58bf5..ad97f67 100644
--- a/src/hw/tpm_drivers.c
+++ b/src/hw/tpm_drivers.c
@@ -374,12 +374,23 @@ static u32 tis_waitrespready(enum tpmDurationType to_t)
     return rc;
 }

+#define CRB_STATE_VALID_STS 0b10000000
+
 /* if device is not there, return '0', '1' otherwise */
 static u32 crb_probe(void)
 {
     if (!CONFIG_TCGBIOS)
         return 0;

+    /* request access -- this must cause a valid STS flag */
+    writeb(CRB_REG(0, CRB_REG_LOC_CTRL), 1);
+
+    /* Wait for the interface to report it's ready */
+    u32 rc = crb_wait_reg(0, CRB_REG_LOC_STATE, TIS2_DEFAULT_TIMEOUT_A,
+                          CRB_STATE_VALID_STS, CRB_STATE_VALID_STS);
+    if (rc)
+        return 0;
+
     u32 ifaceid = readl(CRB_REG(0, CRB_REG_INTF_ID));

if ((ifaceid & 0xf) != 0xf) {