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

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Message-ID: <7032fbfb-8899-d00b-a7fa-811e19d38ce2@nvidia.com>
Date:   Thu, 17 Mar 2022 15:26:28 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Krishna Yarlagadda <kyarlagadda@...dia.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        Ashish Singhal <ashishsingha@...dia.com>
Cc:     Sowjanya Komatineni <skomatineni@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] spi: tegra210-quad: Add wait polling support


On 17/03/2022 09:44, Jon Hunter wrote:
> 
> On 17/03/2022 09:02, Krishna Yarlagadda wrote:
>>> -----Original Message-----
>>> From: Jonathan Hunter <jonathanh@...dia.com>
>>> Sent: 17 March 2022 14:25
>>> To: Krishna Yarlagadda <kyarlagadda@...dia.com>; broonie@...nel.org; 
>>> thierry.reding@...il.com; linux-spi@...r.kernel.org; linux-
>>> tegra@...r.kernel.org; Ashish Singhal <ashishsingha@...dia.com>
>>> Cc: Sowjanya Komatineni <skomatineni@...dia.com>; Laxman Dewangan 
>>> <ldewangan@...dia.com>; robh+dt@...nel.org;
>>> devicetree@...r.kernel.org; linux-kernel@...r.kernel.org
>>> 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@...dia.com>
>>>> ---
>>>>    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