Re: [Patch V5 2/3] tpm_tis-spi: Support hardware wait polling

[Jarkko Sakkinen <jarkko@kernel.org>]

On Tue, Feb 28, 2023 at 03:32:24AM +0000, Krishna Yarlagadda wrote:
> > -----Original Message-----
> > From: Jarkko Sakkinen <jarkko@kernel.org>
> > Sent: 28 February 2023 08:06
> > To: Krishna Yarlagadda <kyarlagadda@nvidia.com>
> > Cc: robh+dt@kernel.org; broonie@kernel.org; peterhuewe@gmx.de;
> > jgg@ziepe.ca; krzysztof.kozlowski+dt@linaro.org; linux-spi@vger.kernel.org;
> > linux-tegra@vger.kernel.org; linux-integrity@vger.kernel.org; linux-
> > kernel@vger.kernel.org; thierry.reding@gmail.com; Jonathan Hunter
> > <jonathanh@nvidia.com>; Sowjanya Komatineni
> > <skomatineni@nvidia.com>; Laxman Dewangan <ldewangan@nvidia.com>
> > Subject: Re: [Patch V5 2/3] tpm_tis-spi: Support hardware wait polling
> > 
> > External email: Use caution opening links or attachments
> > 
> > 
> > On Mon, Feb 27, 2023 at 05:37:01PM +0530, Krishna Yarlagadda wrote:
> > > TPM devices raise wait signal on last addr cycle. This can be detected
> > > by software driver by reading MISO line on same clock which requires
> > > full duplex support. In case of half duplex controllers wait detection
> > > has to be implemented in HW.
> > > Support hardware wait state detection by sending entire message and let
> > > controller handle flow control.
> > 
> > When a is started sentence with the word "support" it translates to "I'm
> > too lazy to write a proper and verbose description of the implementation"
> > :-)
> > 
> > It has some abstract ideas of the implementation, I give you that, but do
> > you think anyone ever will get any value of reading that honestly? A bit
> > more concrette description of the change helps e.g. when bisecting bugs.
> > 
> I presented why we are making the change. Will add explanation on how
> it is implemented as well.

OK, cool, thank you.

> 
> > > QSPI controller in Tegra236 & Tegra241 implement TPM wait polling.
> > >
> > > Signed-off-by: Krishna Yarlagadda <kyarlagadda@nvidia.com>
> > > ---
> > >  drivers/char/tpm/tpm_tis_spi_main.c | 92
> > ++++++++++++++++++++++++++++-
> > >  1 file changed, 90 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/char/tpm/tpm_tis_spi_main.c
> > b/drivers/char/tpm/tpm_tis_spi_main.c
> > > index a0963a3e92bd..5f66448ee09e 100644
> > > --- a/drivers/char/tpm/tpm_tis_spi_main.c
> > > +++ b/drivers/char/tpm/tpm_tis_spi_main.c
> > > @@ -71,8 +71,74 @@ static int tpm_tis_spi_flow_control(struct
> > tpm_tis_spi_phy *phy,
> > >       return 0;
> > >  }
> > >
> > > -int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
> > > -                      u8 *in, const u8 *out)
> > > +/*
> > > + * Half duplex controller with support for TPM wait state detection like
> > > + * Tegra241 need cmd, addr & data sent in single message to manage HW
> > flow
> > > + * control. Each phase sent in different transfer for controller to idenity
> > > + * phase.
> > > + */
> > > +int tpm_tis_spi_hw_flow_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);
> > > +     struct spi_transfer spi_xfer[3];
> > > +     struct spi_message m;
> > > +     u8 transfer_len;
> > > +     int ret;
> > > +
> > > +     while (len) {
> > > +             transfer_len = min_t(u16, len, MAX_SPI_FRAMESIZE);
> > > +
> > > +             spi_message_init(&m);
> > > +             phy->iobuf[0] = (in ? 0x80 : 0) | (transfer_len - 1);
> > > +             phy->iobuf[1] = 0xd4;
> > > +             phy->iobuf[2] = addr >> 8;
> > > +             phy->iobuf[3] = addr;
> > > +
> > > +             memset(&spi_xfer, 0, sizeof(spi_xfer));
> > > +
> > > +             spi_xfer[0].tx_buf = phy->iobuf;
> > > +             spi_xfer[0].len = 1;
> > > +             spi_message_add_tail(&spi_xfer[0], &m);
> > > +
> > > +             spi_xfer[1].tx_buf = phy->iobuf + 1;
> > > +             spi_xfer[1].len = 3;
> > > +             spi_message_add_tail(&spi_xfer[1], &m);
> > > +
> > > +             if (out) {
> > > +                     spi_xfer[2].tx_buf = &phy->iobuf[4];
> > > +                     spi_xfer[2].rx_buf = NULL;
> > > +                     memcpy(&phy->iobuf[4], out, transfer_len);
> > > +                     out += transfer_len;
> > > +             }
> > > +
> > > +             if (in) {
> > > +                     spi_xfer[2].tx_buf = NULL;
> > > +                     spi_xfer[2].rx_buf = &phy->iobuf[4];
> > > +             }
> > > +
> > > +             spi_xfer[2].len = transfer_len;
> > > +             spi_message_add_tail(&spi_xfer[2], &m);
> > > +
> > > +             reinit_completion(&phy->ready);
> > > +
> > > +             ret = spi_sync_locked(phy->spi_device, &m);
> > > +             if (ret < 0)
> > > +                     return ret;
> > > +
> > > +             if (in) {
> > > +                     memcpy(in, &phy->iobuf[4], transfer_len);
> > > +                     in += transfer_len;
> > > +             }
> > > +
> > > +             len -= transfer_len;
> > > +     }
> > > +
> > > +     return ret;
> > > +}
> > > +
> > > +int tpm_tis_spi_sw_flow_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;
> > > @@ -140,6 +206,28 @@ int tpm_tis_spi_transfer(struct tpm_tis_data
> > *data, u32 addr, u16 len,
> > >       return ret;
> > >  }
> > >
> > > +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);
> > > +     struct spi_controller *ctlr = phy->spi_device->controller;
> > > +
> > > +     /*
> > > +      * TPM flow control over SPI requires full duplex support.
> > > +      * Send entire message to a half duplex controller to handle
> > > +      * wait polling in controller.
> > > +      * Set TPM HW flow control flag..
> > > +      */
> > > +     if (ctlr->flags & SPI_CONTROLLER_HALF_DUPLEX) {
> > > +             phy->spi_device->mode |= SPI_TPM_HW_FLOW;
> > > +             return tpm_tis_spi_hw_flow_transfer(data, addr, len, in,
> > > +                                                 out);
> > > +     } else {
> > > +             return tpm_tis_spi_sw_flow_transfer(data, addr, len, in,
> > > +                                                 out);
> > > +     }
> > > +}
> > > +
> > >  static int tpm_tis_spi_read_bytes(struct tpm_tis_data *data, u32 addr,
> > >                                 u16 len, u8 *result, enum tpm_tis_io_mode io_mode)
> > >  {
> > > --
> > > 2.17.1
> > >
> > 
> > Looking pretty good but do you really want to export
> > tpm_tis_spi_{hw,sw}_flow_transfer?
> > 
> > BR, Jarkko
> No need to export tpm_tis_spi_{hw,sw}_flow_transfer as well.
> I will update this in next version.

Great.

BR, Jarkko