linux-kernel - Re: [PATCH v5 2/2] iio: adc: ad4130: add AD4130 driver

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Date:   Thu, 23 Jun 2022 18:27:12 +0300
From:   Cosmin Tanislav <demonsingur@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Cosmin Tanislav <cosmin.tanislav@...log.com>
Subject: Re: [PATCH v5 2/2] iio: adc: ad4130: add AD4130 driver



On 6/20/22 21:29, Andy Shevchenko wrote:
> On Mon, Jun 20, 2022 at 6:27 PM Cosmin Tanislav <demonsingur@...il.com> wrote:
>>
>> AD4130-8 is an ultra-low power, high precision, measurement solution for
>> low bandwidth battery operated applications.
>>
>> The fully integrated AFE (Analog Front-End) includes a multiplexer for up
>> to 16 single-ended or 8 differential inputs, PGA (Programmable Gain
>> Amplifier), 24-bit Sigma-Delta ADC, on-chip reference and oscillator,
>> selectable filter options, smart sequencer, sensor biasing and excitation
>> options, diagnostics, and a FIFO buffer.
> 
> ...
> 
>> +KernelVersion: 5.18
> 
> Are you sure?
> 
> ...
> 
>> +struct ad4130_state {
>> +       struct regmap                   *regmap;
>> +       struct spi_device               *spi;
>> +       struct clk                      *mclk;
>> +       struct regulator_bulk_data      regulators[4];
>> +       u32                             irq_trigger;
>> +       u32                             inv_irq_trigger;
>> +
>> +       /*
>> +        * Synchronize access to members of driver state, and ensure atomicity
> 
> the driver
> 
>> +        * of consecutive regmap operations.
>> +        */
>> +       struct mutex                    lock;
>> +       struct completion               completion;
>> +
>> +       struct iio_chan_spec            chans[AD4130_MAX_CHANNELS];
>> +       struct ad4130_chan_info         chans_info[AD4130_MAX_CHANNELS];
>> +       struct ad4130_slot_info         slots_info[AD4130_MAX_SETUPS];
>> +       enum ad4130_pin_function        pins_fn[AD4130_MAX_ANALOG_PINS];
>> +       u32                             vbias_pins[AD4130_MAX_ANALOG_PINS];
>> +       u32                             num_vbias_pins;
>> +       int                             scale_tbls[AD4130_REF_SEL_MAX][AD4130_MAX_PGA][2];
>> +       struct gpio_chip                gc;
>> +       unsigned int                    gpio_offsets[AD4130_MAX_GPIOS];
>> +       unsigned int                    num_gpios;
>> +
>> +       u32                     int_pin_sel;
>> +       u32                     int_ref_uv;
>> +       u32                     mclk_sel;
>> +       bool                    int_ref_en;
>> +       bool                    bipolar;
>> +
>> +       unsigned int            num_enabled_channels;
>> +       unsigned int            effective_watermark;
>> +       unsigned int            watermark;
>> +
>> +       struct spi_message      fifo_msg;
>> +       struct spi_transfer     fifo_xfer[2];
>> +
>> +       /*
>> +        * DMA (thus cache coherency maintenance) requires the
>> +        * transfer buffers to live in their own cache lines.
>> +        */
> 
> This is a good comment, but what fields does it apply to?

Whatever is below it, grouped together. This is not hard to
understand.

> 
>> +       u8                      reset_buf[AD4130_RESET_BUF_SIZE] __aligned(IIO_DMA_MINALIGN);
>> +       u8                      reg_write_tx_buf[4];
>> +       u8                      reg_read_tx_buf[1];
>> +       u8                      reg_read_rx_buf[3];
>> +       u8                      fifo_tx_buf[2];
>> +       u8                      fifo_rx_buf[AD4130_FIFO_SIZE *
>> +                                           AD4130_FIFO_MAX_SAMPLE_SIZE];
>> +};
> 
> ...
> 
>> +static IIO_DEVICE_ATTR(hwfifo_watermark, 0444, ad4130_get_fifo_watermark, NULL, 0);
>> +static IIO_DEVICE_ATTR(hwfifo_enabled, 0444, ad4130_get_fifo_enabled, NULL, 0);
> 
> IIO_DEVICE_ATTR_RO()
> 
> ...
> 
>> +       for (i = 0; i < st->num_gpios; i++)
>> +               val |= BIT(st->gpio_offsets[i]);
> 
> This might overflow.

No it might not. num_gpios is at max AD4130_MAX_GPIOS, which is 4.

> 
> ...
> 
>> +       for (i = 0; i < st->num_vbias_pins; i++)
>> +               val |= BIT(st->vbias_pins[i]);
> 
> Ditto.

No it might not. num_vbias_pins is at max AD4130_MAX_ANALOG_PINS, which
is 16.

> 
> ...
> 
>> +       st->regmap = devm_regmap_init(dev, NULL, st, &ad4130_regmap_config);
>> +       if (IS_ERR(st->regmap))
>> +               return PTR_ERR(st->regmap);
> 
> Can it use regular regmap SPI?

No. I'm pretty sure I've already talked about this.

>