On Sun, Mar 26, 2023 at 12:04:07AM +0530, Krishna Yarlagadda wrote: > TPM specification [1] defines flow control over SPI. Client device can > insert a wait state on MISO when address is transmitted by controller > on MOSI. Detecting the wait state in software is only possible for > full duplex controllers. For controllers that support only half- > duplex, the wait state detection needs to be implemented in hardware. > > Add a flag SPI_TPM_HW_FLOW for TPM device to set when software flow > control is not possible and hardware flow control is expected from > SPI controller. > > Reference: > [1] https://trustedcomputinggroup.org/resource/pc-client-work-group- > pc-client-specific-tpm-interface-specification-tis/ > > Signed-off-by: Krishna Yarlagadda <kyarlagadda@xxxxxxxxxx> > --- > include/linux/spi/spi.h | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > > diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h > index 873ced6ae4ca..cfe42f8cd7a4 100644 > --- a/include/linux/spi/spi.h > +++ b/include/linux/spi/spi.h > @@ -184,8 +184,18 @@ struct spi_device { > u8 chip_select; > u8 bits_per_word; > bool rt; > -#define SPI_NO_TX BIT(31) /* No transmit wire */ > -#define SPI_NO_RX BIT(30) /* No receive wire */ > +#define SPI_NO_TX BIT(31) /* No transmit wire */ > +#define SPI_NO_RX BIT(30) /* No receive wire */ > + /* > + * TPM specification defines flow control over SPI. Client device > + * can insert a wait state on MISO when address is transmitted by > + * controller on MOSI. Detecting the wait state in software is only > + * possible for full duplex controllers. For controllers that support > + * only half-duplex, the wait state detection needs to be implemented > + * in hardware. TPM devices would set this flag when hardware flow > + * control is expected from SPI controller. > + */ > +#define SPI_TPM_HW_FLOW BIT(29) /* TPM HW flow control */ > /* > * All bits defined above should be covered by SPI_MODE_KERNEL_MASK. > * The SPI_MODE_KERNEL_MASK has the SPI_MODE_USER_MASK counterpart, > @@ -195,7 +205,7 @@ struct spi_device { > * These bits must not overlap. A static assert check should make sure of that. > * If adding extra bits, make sure to decrease the bit index below as well. > */ > -#define SPI_MODE_KERNEL_MASK (~(BIT(30) - 1)) > +#define SPI_MODE_KERNEL_MASK (~(BIT(29) - 1)) > u32 mode; > int irq; > void *controller_state; > -- > 2.17.1 > Acked-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> BR, Jarkko
