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

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Date:   Sun, 9 Oct 2022 18:31:22 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Cosmin Tanislav <demonsingur@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-iio@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Cosmin Tanislav <cosmin.tanislav@...log.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH v9 2/2] iio: adc: ad4130: add AD4130 driver

On Thu,  6 Oct 2022 17:07:37 +0300
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.
> 
> Signed-off-by: Cosmin Tanislav <cosmin.tanislav@...log.com>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.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.


> +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?

> +	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?


> +
> +	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);
> +}
> +