char: tpm: add i2c driver for cr50

Add TPM 2.0 compatible I2C interface for chips with cr50 firmware.

The firmware running on the currently supported H1 MCU requires a
special driver to handle its specific protocol, and this makes it
unsuitable to use tpm_tis_core_* and instead it must implement the
underlying TPM protocol similar to the other I2C TPM drivers.

- All 4 bytes of status register must be read/written at once.
- FIFO and burst count is limited to 63 and must be drained by AP.
- Provides an interrupt to indicate when read response data is ready
and when the TPM is finished processing write data.

This driver is based on the existing infineon I2C TPM driver, which
most closely matches the cr50 i2c protocol behavior.
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Fabien Lahoudere <fabien.lahoudere@collabora.com>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Tested-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

drivers/char/tpm/Kconfig

@@ -86,6 +86,16 @@ config TCG_TIS_SYNQUACER
 	  To compile this driver as a module, choose  M here;
 	  the module will be called tpm_tis_synquacer.
 
+config TCG_TIS_I2C_CR50
+	tristate "TPM Interface Specification 2.0 Interface (I2C - CR50)"
+	depends on I2C
+	select TCG_CR50
+	help
+	  This is a driver for the Google cr50 I2C TPM interface which is a
+	  custom microcontroller and requires a custom i2c protocol interface
+	  to handle the limitations of the hardware.  To compile this driver
+	  as a module, choose M here; the module will be called tcg_tis_i2c_cr50.
+
 config TCG_TIS_I2C_ATMEL
 	tristate "TPM Interface Specification 1.2 Interface (I2C - Atmel)"
 	depends on I2C

drivers/char/tpm/Makefile

@@ -27,6 +27,8 @@ obj-$(CONFIG_TCG_TIS_SPI) += tpm_tis_spi.o
 tpm_tis_spi-y := tpm_tis_spi_main.o
 tpm_tis_spi-$(CONFIG_TCG_TIS_SPI_CR50) += tpm_tis_spi_cr50.o
 
+obj-$(CONFIG_TCG_TIS_I2C_CR50) += tpm_tis_i2c_cr50.o
+
 obj-$(CONFIG_TCG_TIS_I2C_ATMEL) += tpm_i2c_atmel.o
 obj-$(CONFIG_TCG_TIS_I2C_INFINEON) += tpm_i2c_infineon.o
 obj-$(CONFIG_TCG_TIS_I2C_NUVOTON) += tpm_i2c_nuvoton.o