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

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Date:   Mon, 19 Aug 2019 19:35:05 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Peter Huewe <peterhuewe@....de>, linux-kernel@...r.kernel.org,
        linux-integrity@...r.kernel.org,
        Andrey Pronin <apronin@...omium.org>,
        Duncan Laurie <dlaurie@...omium.org>,
        Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <groeck@...omium.org>,
        Alexander Steffen <Alexander.Steffen@...ineon.com>
Subject: Re: [PATCH v4 3/6] tpm: tpm_tis_spi: Add a pre-transfer callback

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@...omium.org>
> Cc: Duncan Laurie <dlaurie@...omium.org>
> Cc: Jason Gunthorpe <jgg@...pe.ca>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Guenter Roeck <groeck@...omium.org>
> Cc: Alexander Steffen <Alexander.Steffen@...ineon.com>
> Signed-off-by: Stephen Boyd <swboyd@...omium.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