tpm/st33zp24/spi: Improve st33zp24_spi_evaluate_latency

Add check in st33zp24_spi_evaluate_latency helping to diagnose if the chip
is present or in a bad state.

Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/char/tpm/st33zp24/spi.c b/drivers/char/tpm/st33zp24/spi.c
index 08e6bf54d7dd..a2ef8ec4ba80 100644
--- a/drivers/char/tpm/st33zp24/spi.c
+++ b/drivers/char/tpm/st33zp24/spi.c
@@ -214,6 +214,11 @@ static int st33zp24_spi_evaluate_latency(void *phy_id)
                                                 &data, 1);
                 latency++;
         }
+        if (status < 0)
+                return status;
+        if (latency == MAX_SPI_LATENCY)
+                return -ENODEV;
+
         return latency - 1;
 } /* evaluate_latency() */