tpm: tpm_tis_spi: Introduce a flow control callback

Cr50 firmware has a different flow control protocol than the one used by
this TPM PTP SPI driver. Introduce a flow control callback so we can
override the standard sequence with the custom one that Cr50 uses.

Cc: Andrey Pronin <apronin@chromium.org>
Cc: Duncan Laurie <dlaurie@chromium.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Alexander Steffen <Alexander.Steffen@infineon.com>
Cc: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

diff --git a/drivers/char/tpm/tpm_tis_spi.c b/drivers/char/tpm/tpm_tis_spi.c
index 19513e62205324c26c81e0ba8e759768de1838c6..b3ed85671dd84468f1d57b94ee4d7342be9f7e9a 100644 (file)
--- a/drivers/char/tpm/tpm_tis_spi.c
+++ b/drivers/char/tpm/tpm_tis_spi.c
@@ -42,6 +42,8 @@
 struct tpm_tis_spi_phy {
        struct tpm_tis_data priv;
        struct spi_device *spi_device;
+       int (*flow_control)(struct tpm_tis_spi_phy *phy,
+                           struct spi_transfer *xfer);
        u8 *iobuf;
 };
 
@@ -50,12 +52,46 @@ static inline struct tpm_tis_spi_phy *to_tpm_tis_spi_phy(struct tpm_tis_data *da
        return container_of(data, struct tpm_tis_spi_phy, priv);
 }
 
+/*
+ * TCG SPI flow control is documented in section 6.4 of the spec[1]. In short,
+ * keep trying to read from the device until MISO goes high indicating the
+ * wait state has ended.
+ *
+ * [1] https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
+ */
+static int tpm_tis_spi_flow_control(struct tpm_tis_spi_phy *phy,
+                                   struct spi_transfer *spi_xfer)
+{
+       struct spi_message m;
+       int ret, i;
+
+       if ((phy->iobuf[3] & 0x01) == 0) {
+               // handle SPI wait states
+               phy->iobuf[0] = 0;
+
+               for (i = 0; i < TPM_RETRY; i++) {
+                       spi_xfer->len = 1;
+                       spi_message_init(&m);
+                       spi_message_add_tail(spi_xfer, &m);
+                       ret = spi_sync_locked(phy->spi_device, &m);
+                       if (ret < 0)
+                               return ret;
+                       if (phy->iobuf[0] & 0x01)
+                               break;
+               }
+
+               if (i == TPM_RETRY)
+                       return -ETIMEDOUT;
+       }
+
+       return 0;
+}
+
 static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
                                u8 *in, const u8 *out)
 {
        struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
        int ret = 0;
-       int i;
        struct spi_message m;
        struct spi_transfer spi_xfer;
        u8 transfer_len;
@@ -82,26 +118,9 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
                if (ret < 0)
                        goto exit;
 
-               if ((phy->iobuf[3] & 0x01) == 0) {
-                       // handle SPI wait states
-                       phy->iobuf[0] = 0;
-
-                       for (i = 0; i < TPM_RETRY; i++) {
-                               spi_xfer.len = 1;
-                               spi_message_init(&m);
-                               spi_message_add_tail(&spi_xfer, &m);
-                               ret = spi_sync_locked(phy->spi_device, &m);
-                               if (ret < 0)
-                                       goto exit;
-                               if (phy->iobuf[0] & 0x01)
-                                       break;
-                       }
-
-                       if (i == TPM_RETRY) {
-                               ret = -ETIMEDOUT;
-                               goto exit;
-                       }
-               }
+               ret = phy->flow_control(phy, &spi_xfer);
+               if (ret < 0)
+                       goto exit;
 
                spi_xfer.cs_change = 0;
                spi_xfer.len = transfer_len;
@@ -207,6 +226,7 @@ static int tpm_tis_spi_probe(struct spi_device *dev)
        phy->iobuf = devm_kmalloc(&dev->dev, MAX_SPI_FRAMESIZE, GFP_KERNEL);
        if (!phy->iobuf)
                return -ENOMEM;
+       phy->flow_control = tpm_tis_spi_flow_control;
 
        /* If the SPI device has an IRQ then use that */
        if (dev->irq > 0)