iio: at91-sama5d2_adc: remove usage of iio_priv_to_dev() helper

We may want to get rid of the iio_priv_to_dev() helper. The reason is that
we will hide some of the members of the iio_dev structure (to prevent
drivers from accessing them directly), and that will also mean hiding the
implementation of the iio_priv_to_dev() helper inside the IIO core.

Hiding the implementation of iio_priv_to_dev() implies that some fast-paths
may not be fast anymore, so a general idea is to try to get rid of the
iio_priv_to_dev() altogether.
The iio_priv() helper won't be affected by the rework, as the iio_dev
struct will keep a reference to the private information.

For this driver, not using iio_priv_to_dev(), means reworking some paths to
pass the iio device and using iio_priv() to access the private information,
and also keeping a reference to the iio device for some quirky paths.

One [quirky] path is the at91_adc_workq_handler() which requires the IIO
device & the state struct to push to buffers.
Since this requires the back-ref to the IIO device, the
at91_adc_touch_pos() also uses it. This simplifies the patch a bit. The
information required in this function is mostly for debugging purposes.
Replacing it with a reference to the IIO device would have been a slightly
bigger change, which may not be worth it (for just the debugging purpose
and given that we need the back-ref to the IIO device anyway).
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/at91-sama5d2_adc.c

@@ -402,6 +402,7 @@ struct at91_adc_state {
 	wait_queue_head_t		wq_data_available;
 	struct at91_adc_dma		dma_st;
 	struct at91_adc_touch		touch_st;
+	struct iio_dev			*indio_dev;
 	u16				buffer[AT91_BUFFER_MAX_HWORDS];
 	/*
 	 * lock to prevent concurrent 'single conversion' requests through
@@ -642,13 +643,13 @@ static u16 at91_adc_touch_pos(struct at91_adc_state *st, int reg)
 	/* first half of register is the x or y, second half is the scale */
 	val = at91_adc_readl(st, reg);
 	if (!val)
-		dev_dbg(&iio_priv_to_dev(st)->dev, "pos is 0\n");
+		dev_dbg(&st->indio_dev->dev, "pos is 0\n");
 
 	pos = val & AT91_SAMA5D2_XYZ_MASK;
 	result = (pos << AT91_SAMA5D2_MAX_POS_BITS) - pos;
 	scale = (val >> 16) & AT91_SAMA5D2_XYZ_MASK;
 	if (scale == 0) {
-		dev_err(&iio_priv_to_dev(st)->dev, "scale is 0\n");
+		dev_err(&st->indio_dev->dev, "scale is 0\n");
 		return 0;
 	}
 	result /= scale;
@@ -1186,9 +1187,9 @@ static unsigned at91_adc_startup_time(unsigned startup_time_min,
 	return i;
 }
 
-static void at91_adc_setup_samp_freq(struct at91_adc_state *st, unsigned freq)
+static void at91_adc_setup_samp_freq(struct iio_dev *indio_dev, unsigned freq)
 {
-	struct iio_dev *indio_dev = iio_priv_to_dev(st);
+	struct at91_adc_state *st = iio_priv(indio_dev);
 	unsigned f_per, prescal, startup, mr;
 
 	f_per = clk_get_rate(st->per_clk);
@@ -1257,9 +1258,9 @@ static void at91_adc_pen_detect_interrupt(struct at91_adc_state *st)
 	st->touch_st.touching = true;
 }
 
-static void at91_adc_no_pen_detect_interrupt(struct at91_adc_state *st)
+static void at91_adc_no_pen_detect_interrupt(struct iio_dev *indio_dev)
 {
-	struct iio_dev *indio_dev = iio_priv_to_dev(st);
+	struct at91_adc_state *st = iio_priv(indio_dev);
 
 	at91_adc_writel(st, AT91_SAMA5D2_TRGR,
 			AT91_SAMA5D2_TRGR_TRGMOD_NO_TRIGGER);
@@ -1279,7 +1280,7 @@ static void at91_adc_workq_handler(struct work_struct *workq)
 					struct at91_adc_touch, workq);
 	struct at91_adc_state *st = container_of(touch_st,
 					struct at91_adc_state, touch_st);
-	struct iio_dev *indio_dev = iio_priv_to_dev(st);
+	struct iio_dev *indio_dev = st->indio_dev;
 
 	iio_push_to_buffers(indio_dev, st->buffer);
 }
@@ -1300,7 +1301,7 @@ static irqreturn_t at91_adc_interrupt(int irq, void *private)
 		at91_adc_pen_detect_interrupt(st);
 	} else if ((status & AT91_SAMA5D2_IER_NOPEN)) {
 		/* nopen detected IRQ */
-		at91_adc_no_pen_detect_interrupt(st);
+		at91_adc_no_pen_detect_interrupt(indio);
 	} else if ((status & AT91_SAMA5D2_ISR_PENS) &&
 		   ((status & rdy_mask) == rdy_mask)) {
 		/* periodic trigger IRQ - during pen sense */
@@ -1468,7 +1469,7 @@ static int at91_adc_write_raw(struct iio_dev *indio_dev,
 		    val > st->soc_info.max_sample_rate)
 			return -EINVAL;
 
-		at91_adc_setup_samp_freq(st, val);
+		at91_adc_setup_samp_freq(indio_dev, val);
 		return 0;
 	default:
 		return -EINVAL;
@@ -1606,8 +1607,10 @@ static int at91_adc_update_scan_mode(struct iio_dev *indio_dev,
 	return 0;
 }
 
-static void at91_adc_hw_init(struct at91_adc_state *st)
+static void at91_adc_hw_init(struct iio_dev *indio_dev)
 {
+	struct at91_adc_state *st = iio_priv(indio_dev);
+
 	at91_adc_writel(st, AT91_SAMA5D2_CR, AT91_SAMA5D2_CR_SWRST);
 	at91_adc_writel(st, AT91_SAMA5D2_IDR, 0xffffffff);
 	/*
@@ -1617,7 +1620,7 @@ static void at91_adc_hw_init(struct at91_adc_state *st)
 	at91_adc_writel(st, AT91_SAMA5D2_MR,
 			AT91_SAMA5D2_MR_TRANSFER(2) | AT91_SAMA5D2_MR_ANACH);
 
-	at91_adc_setup_samp_freq(st, st->soc_info.min_sample_rate);
+	at91_adc_setup_samp_freq(indio_dev, st->soc_info.min_sample_rate);
 
 	/* configure extended mode register */
 	at91_adc_config_emr(st);
@@ -1699,6 +1702,7 @@ static int at91_adc_probe(struct platform_device *pdev)
 	indio_dev->num_channels = ARRAY_SIZE(at91_adc_channels);
 
 	st = iio_priv(indio_dev);
+	st->indio_dev = indio_dev;
 
 	bitmap_set(&st->touch_st.channels_bitmask,
 		   AT91_SAMA5D2_TOUCH_X_CHAN_IDX, 1);
@@ -1810,7 +1814,7 @@ static int at91_adc_probe(struct platform_device *pdev)
 		goto vref_disable;
 	}
 
-	at91_adc_hw_init(st);
+	at91_adc_hw_init(indio_dev);
 
 	ret = clk_prepare_enable(st->per_clk);
 	if (ret)
@@ -1926,7 +1930,7 @@ static __maybe_unused int at91_adc_resume(struct device *dev)
 	if (ret)
 		goto vref_disable_resume;
 
-	at91_adc_hw_init(st);
+	at91_adc_hw_init(indio_dev);
 
 	/* reconfiguring trigger hardware state */
 	if (!iio_buffer_enabled(indio_dev))