Re: [PATCH v9 2/2] iio: adc: ad4130: add AD4130 driver

Cosmin Tanislav
2022-10-17T07:08:14Z

On 10/9/22 20:31, Jonathan Cameron wrote:
> On Thu, 6 Oct 2022 17:07:37 +0300
> Cosmin Tanislav <demonsingur@gmail.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.
>>
>> Signed-off-by: Cosmin Tanislav <cosmin.tanislav@analog.com>
>> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> Hi Cosmin,
>
> I've cropped down (mostly) to the clock changes.
> A few minor things in there + this looks like it would suffer from the issue
> with IIO_CONST_ATTR() not being handled correctly for buffer attributes.
>
> Jonathan
>
>
>
>> +static IIO_CONST_ATTR(hwfifo_watermark_min, "1");
>> +static IIO_CONST_ATTR(hwfifo_watermark_max, __stringify(AD4130_FIFO_SIZE));
>
> These look like they'd suffer from same problem
> https://lore.kernel.org/all/cover.1664782676.git.mazziesaccount@gmail.com/
> tackles. Short term fix is don't use IIO_CONST_ATTR for buffer attributes.
>

Right, this only works downstream.

Should I switch to IIO_STATIC_CONST_DEVICE_ATTR?

>
>> +static IIO_DEVICE_ATTR_RO(hwfifo_watermark, 0);
>> +static IIO_DEVICE_ATTR_RO(hwfifo_enabled, 0);
>> +
>> +static const struct attribute *ad4130_fifo_attributes[] = {
>> + &iio_const_attr_hwfifo_watermark_min.dev_attr.attr,
>> + &iio_const_attr_hwfifo_watermark_max.dev_attr.attr,
>> + &iio_dev_attr_hwfifo_watermark.dev_attr.attr,
>> + &iio_dev_attr_hwfifo_enabled.dev_attr.attr,
>> + NULL
>> +};
>
>
>> +static void ad4130_clk_disable_unprepare(void *clk)
>> +{
>> + clk_disable_unprepare(clk);
>> +}
>> +
>> +static int ad4130_set_mclk_sel(struct ad4130_state *st,
>> + enum ad4130_mclk_sel mclk_sel)
>> +{
>> + return regmap_update_bits(st->regmap, AD4130_ADC_CONTROL_REG,
>> + AD4130_ADC_CONTROL_MCLK_SEL_MASK,
>> + FIELD_PREP(AD4130_ADC_CONTROL_MCLK_SEL_MASK,
>> + mclk_sel));
>> +}
>> +
>> +static unsigned long ad4130_int_clk_recalc_rate(struct clk_hw *hw,
>> + unsigned long parent_rate)
>> +{
>> + return AD4130_MCLK_FREQ_76_8KHZ;
>> +}
>> +
>> +static int ad4130_int_clk_is_enabled(struct clk_hw *hw)
>> +{
>> + struct ad4130_state *st = container_of(hw, struct ad4130_state, int_clk_hw);
>> +
>> + return st->mclk_sel == AD4130_MCLK_76_8KHZ_OUT;
>> +}
>> +
>> +static int ad4130_int_clk_prepare(struct clk_hw *hw)
>> +{
>> + struct ad4130_state *st = container_of(hw, struct ad4130_state, int_clk_hw);
>> + int ret;
>> +
>> + ret = ad4130_set_mclk_sel(st, AD4130_MCLK_76_8KHZ_OUT);
>> + if (ret)
>> + return ret;
>> +
>> + st->mclk_sel = AD4130_MCLK_76_8KHZ_OUT;
>> +
>> + return 0;
>> +}
>> +
>> +static void ad4130_int_clk_unprepare(struct clk_hw *hw)
>> +{
>> + struct ad4130_state *st = container_of(hw, struct ad4130_state, int_clk_hw);
>> + int ret;
>> +
>> + ret = ad4130_set_mclk_sel(st, AD4130_MCLK_76_8KHZ);
>> + if (ret)
>> + return;
>> +
>> + st->mclk_sel = AD4130_MCLK_76_8KHZ;
>> +}
>> +
>> +static const struct clk_ops ad4130_int_clk_ops = {
>> + .recalc_rate = ad4130_int_clk_recalc_rate,
>> + .is_enabled = ad4130_int_clk_is_enabled,
>> + .prepare = ad4130_int_clk_prepare,
>> + .unprepare = ad4130_int_clk_unprepare,
>> +};
>> +
>> +static int ad4130_setup_int_clk(struct ad4130_state *st)
>> +{
>> + struct device *dev = &st->spi->dev;
>> + struct device_node *of_node = dev->of_node;
>
> Hmm. There goes our careful use of generic firmware properties.
> I guess there still isn't much we can do about that for clks
> so at least it's contained to this one function.
>
> Also is this code safe to of_node == NULL?
>

No, I guess it is not. I'll fix it.
Should I just
if (!of_node) return 0;
?

>> + struct clk_init_data init;
>> + const char *clk_name;
>> + struct clk *clk;
>> +
>> + if (st->int_pin_sel == AD4130_INT_PIN_CLK ||
>> + st->mclk_sel != AD4130_MCLK_76_8KHZ)
>> + return 0;
>> +
>> + clk_name = of_node->name;
>> + of_property_read_string(of_node, "clock-output-names", &clk_name);
>
> Probably want to check success of that read before using it.
> I'd also expect that these to be optional + doesn't he dt binding need
> updating to add this stuff?
>

It does need updating, sorry.
of_node->name is the default clk_name, if clock-output-names is present
then the of_property_read_string() result will be used instead. If not,
there's no trouble, and we don't care about the return value since we
have the default clk_name assigned just above.
I can also switch to device_property_read_string() here to minimize the
damage from using OF.

>
>> +
>> + init.name = clk_name;
>> + init.ops = &ad4130_int_clk_ops;
>> +
>> + st->int_clk_hw.init = &init;
>> + clk = devm_clk_register(dev, &st->int_clk_hw);
>> + if (IS_ERR(clk))
>> + return PTR_ERR(clk);
>> +
>> + return of_clk_add_provider(of_node, of_clk_src_simple_get, clk);
>> +}
>> +