Commit 8ab5e82a authored by Stephen Boyd's avatar Stephen Boyd Committed by Jarkko Sakkinen
Browse files

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: default avatarStephen Boyd <swboyd@chromium.org>
Tested-by: default avatarHeiko Stuebner <heiko@sntech.de>
Reviewed-by: default avatarHeiko Stuebner <heiko@sntech.de>
Reviewed-by: default avatarJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: default avatarJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
parent 2e2ee5a2

drivers/char/tpm/tpm_tis_spi.c

+41 −21
Original line number Diff line number Diff line
@@ -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);

		ret = phy->flow_control(phy, &spi_xfer);

		if (ret < 0)

			goto exit;

				if (phy->iobuf[0] & 0x01)

					break;

			}



			if (i == TPM_RETRY) {

				ret = -ETIMEDOUT;

				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)

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