Re: [PATCH 2/3] spi: tegra210-quad: Add wait polling support

[Jon Hunter <jonathanh@xxxxxxxxxx>]

On 17/03/2022 09:44, Jon Hunter wrote:
> On 17/03/2022 09:02, Krishna Yarlagadda wrote:
> > > -----Original Message-----
> > > From: Jonathan Hunter <jonathanh@xxxxxxxxxx>
> > > Sent: 17 March 2022 14:25
> > > To: Krishna Yarlagadda <kyarlagadda@xxxxxxxxxx>; broonie@xxxxxxxxxx; 
> > > thierry.reding@xxxxxxxxx; linux-spi@xxxxxxxxxxxxxxx; linux-
> > > tegra@xxxxxxxxxxxxxxx; Ashish Singhal <ashishsingha@xxxxxxxxxx>
> > > Cc: Sowjanya Komatineni <skomatineni@xxxxxxxxxx>; Laxman Dewangan 
> > > <ldewangan@xxxxxxxxxx>; robh+dt@xxxxxxxxxx;
> > > devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> > > Subject: Re: [PATCH 2/3] spi: tegra210-quad: Add wait polling support
> > >
> > >
> > > On 17/03/2022 01:20, Krishna Yarlagadda wrote:
> > > > Controller can poll for wait state inserted by TPM device and
> > > > handle it.
> > > >
> > > > Signed-off-by: Krishna Yarlagadda <kyarlagadda@xxxxxxxxxx>
> > > > ---
> > > >    drivers/spi/spi-tegra210-quad.c | 31 +++++++++++++++++++++++++++++++
> > > >    1 file changed, 31 insertions(+)
> > > >
> > > > diff --git a/drivers/spi/spi-tegra210-quad.c 
> > > > b/drivers/spi/spi-tegra210-quad.c
> > > > index a2e225e8f7f0..ecf171bfcdce 100644
> > > > --- a/drivers/spi/spi-tegra210-quad.c
> > > > +++ b/drivers/spi/spi-tegra210-quad.c
> > > > @@ -142,6 +142,7 @@
> > > >
> > > >    #define QSPI_GLOBAL_CONFIG            0X1a4
> > > >    #define QSPI_CMB_SEQ_EN                BIT(0)
> > > > +#define QSPI_TPM_WAIT_POLL_EN            BIT(1)
> > > >
> > > >    #define QSPI_CMB_SEQ_ADDR            0x1a8
> > > >    #define QSPI_ADDRESS_VALUE_SET(X)        (((x) & 0xFFFF) << 0)
> > > > @@ -165,11 +166,13 @@ struct tegra_qspi_soc_data {
> > > >        bool has_dma;
> > > >        bool cmb_xfer_capable;
> > > >        bool cs_count;
> > > > +    bool has_wait_polling;
> > > >    };
> > > >
> > > >    struct tegra_qspi_client_data {
> > > >        int tx_clk_tap_delay;
> > > >        int rx_clk_tap_delay;
> > > > +    bool wait_polling;
> > > >    };
> > > >
> > > >    struct tegra_qspi {
> > > > @@ -833,6 +836,11 @@ static u32 tegra_qspi_setup_transfer_one(struct 
> > > > spi_device *spi, struct spi_tran
> > > >            else
> > > >                command1 |= QSPI_CONTROL_MODE_0;
> > > >
> > > > +        if (tqspi->soc_data->cmb_xfer_capable)
> > > > +            command1 &= ~QSPI_CS_SW_HW;
> > > > +        else
> > > > +            command1 |= QSPI_CS_SW_HW;
> > > > +
> > > >            if (spi->mode & SPI_CS_HIGH)
> > > >                command1 |= QSPI_CS_SW_VAL;
> > > >            else
> > > > @@ -917,6 +925,7 @@ static int tegra_qspi_start_transfer_one(struct 
> > > > spi_device *spi,
> > > >
> > > >    static struct tegra_qspi_client_data 
> > > > *tegra_qspi_parse_cdata_dt(struct spi_device *spi)
> > > >    {
> > > > +    struct tegra_qspi *tqspi = spi_master_get_devdata(spi->master);
> > > >        struct tegra_qspi_client_data *cdata;
> > > >
> > > >        cdata = devm_kzalloc(&spi->dev, sizeof(*cdata), GFP_KERNEL);
> > > > @@ -927,6 +936,11 @@ static struct tegra_qspi_client_data 
> > > > *tegra_qspi_parse_cdata_dt(struct spi_devic
> > > >                     &cdata->tx_clk_tap_delay);
> > > >        device_property_read_u32(&spi->dev, "nvidia,rx-clk-tap-delay",
> > > >                     &cdata->rx_clk_tap_delay);
> > > > +    if (tqspi->soc_data->has_wait_polling)
> > > > +        cdata->wait_polling = device_property_read_bool
> > > > +                    (&spi->dev,
> > > > +                     "nvidia,wait-polling");
> > > > +
> > >
> > >
> > > This looks odd. Why do we need this device-tree property if it is
> > > already specified in the SoC data?
> > Soc data specifies chip is capable of wait-polling.
> > Wait polling still has to be selected on slave devices that can 
> > support it.
> > I will add one line description for the properties in next version.
>
>
> I can't say I am familiar with this, but it seems that the ideal 
> solution would be able to detect if this needs to be enabled depending 
> on the device connected. Is that not possible?

Also, given that Grace supports 4 chip-selects per device, how does this 
work if there is TPM connected to one chip-select and something else 
connected to another?

Jon

--
nvpublic