Re: [PATCH v4 3/6] tpm: tpm_tis_spi: Add a pre-transfer callback

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Mon, Aug 12, 2019 at 03:36:19PM -0700, Stephen Boyd wrote:
> Cr50 firmware has a requirement to wait for the TPM to wakeup before
> sending commands over the SPI bus. Otherwise, the firmware could be in
> deep sleep and not respond. Add a hook to tpm_tis_spi_transfer() before
> we start a SPI transfer so we can keep track of the last time the TPM
> driver accessed the SPI bus.
> 
> 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 | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm_tis_spi.c b/drivers/char/tpm/tpm_tis_spi.c
> index 819602e85b34..93f49b1941f0 100644
> --- a/drivers/char/tpm/tpm_tis_spi.c
> +++ b/drivers/char/tpm/tpm_tis_spi.c
> @@ -44,6 +44,7 @@ struct tpm_tis_spi_phy {
>  	struct spi_device *spi_device;
>  	int (*flow_control)(struct tpm_tis_spi_phy *phy,
>  			    struct spi_transfer *xfer);
> +	void (*pre_transfer)(struct tpm_tis_spi_phy *phy);

A callback should have somewhat well defined purpose. A callback named
as pre_transfer() could have any purpose.

/Jarkko