diff mbox series

[v4,2/6] tpm: tpm_tis_spi: Introduce a flow control callback

Message ID 20190812223622.73297-3-swboyd@chromium.org
State New
Headers show
Series tpm: Add driver for cr50 | expand

Commit Message

Stephen Boyd Aug. 12, 2019, 10:36 p.m. UTC
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>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 drivers/char/tpm/tpm_tis_spi.c | 55 +++++++++++++++++++++-------------
 1 file changed, 34 insertions(+), 21 deletions(-)

Comments

Jarkko Sakkinen Aug. 19, 2019, 4:32 p.m. UTC | #1
On Mon, Aug 12, 2019 at 03:36:18PM -0700, Stephen Boyd wrote:
> 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>
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> ---
>  drivers/char/tpm/tpm_tis_spi.c | 55 +++++++++++++++++++++-------------
>  1 file changed, 34 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_spi.c b/drivers/char/tpm/tpm_tis_spi.c
> index 19513e622053..819602e85b34 100644
> --- 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 +52,39 @@ 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);
>  }
>  
> +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;
> +}

AFAIK the flow control is not part of the SPI standard itself but is
proprietary for each slave device. Thus, the flow control should be
documented to the source code. I do not want flow control mechanisms to
be multiplied before this is done.

The magic number 0x01 would be also good to get rid off.

/Jarkko
Stephen Boyd Aug. 19, 2019, 5:06 p.m. UTC | #2
Quoting Jarkko Sakkinen (2019-08-19 09:32:40)
> On Mon, Aug 12, 2019 at 03:36:18PM -0700, Stephen Boyd wrote:
> > 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>
> > Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> > ---
> >  drivers/char/tpm/tpm_tis_spi.c | 55 +++++++++++++++++++++-------------
> >  1 file changed, 34 insertions(+), 21 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm_tis_spi.c b/drivers/char/tpm/tpm_tis_spi.c
> > index 19513e622053..819602e85b34 100644
> > --- 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 +52,39 @@ 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);
> >  }
> >  
> > +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;
> > +}
> 
> AFAIK the flow control is not part of the SPI standard itself but is
> proprietary for each slave device. Thus, the flow control should be
> documented to the source code. I do not want flow control mechanisms to
> be multiplied before this is done.

Can you clarify this please? I don't understand what "the flow control
should be documented to the source code" means.

> 
> The magic number 0x01 would be also good to get rid off.
> 

Ok. What name should the #define be? I can make that another patch.
Jarkko Sakkinen Aug. 21, 2019, 6:13 p.m. UTC | #3
On Mon, Aug 19, 2019 at 10:06:40AM -0700, Stephen Boyd wrote:
> > AFAIK the flow control is not part of the SPI standard itself but is
> > proprietary for each slave device. Thus, the flow control should be
> > documented to the source code. I do not want flow control mechanisms to
> > be multiplied before this is done.
> 
> Can you clarify this please? I don't understand what "the flow control
> should be documented to the source code" means.

Off the top of my head:

/* TCG SPI flow control is documented in the section 6.4 of [1]. However,
 * Google's CR50 chip has its own proprietary flow control. This struct
 * is used to bind the appropriate flow control mechanism.
 *
 * [1] https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
 */

> > 
> > The magic number 0x01 would be also good to get rid off.
> > 
> 
> Ok. What name should the #define be? I can make that another patch.

Do nothing. Not part of your patch set scope, was a stupid comment from
my side.

/Jarkko
diff mbox series

Patch

diff --git a/drivers/char/tpm/tpm_tis_spi.c b/drivers/char/tpm/tpm_tis_spi.c
index 19513e622053..819602e85b34 100644
--- 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 +52,39 @@  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);
 }
 
+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 +111,9 @@  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 +219,7 @@  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)