iio: adc: at91-sama5d2_adc: add helper for COR register

Add helper for the COR register. This helper allows to modify the COR
register, removes duplicate code and improves readability.
The COR offset is now part of the register layout. This will allow
different platform with a different offset to use the same helper.
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Link: https://lore.kernel.org/r/20210901123013.329792-7-eugen.hristev@microchip.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/at91-sama5d2_adc.c

@@ -151,8 +151,8 @@ struct at91_adc_reg_layout {
 	u16				CGR;
 /* Channel Offset Register */
 	u16				COR;
-#define AT91_SAMA5D2_COR_DIFF_OFFSET	16
-
+/* Channel Offset Register differential offset - constant, not a register */
+	u16				COR_diff_offset;
 /* Analog Control Register */
 	u16				ACR;
 /* Analog Control Register - Pen detect sensitivity mask */
@@ -246,6 +246,7 @@ static const struct at91_adc_reg_layout sama5d2_layout = {
 	.CWR =			0x44,
 	.CGR =			0x48,
 	.COR =			0x4c,
+	.COR_diff_offset =	16,
 	.ACR =			0x94,
 	.TSMR =			0xb0,
 	.XPOSR =		0xb4,
@@ -594,6 +595,21 @@ static unsigned int at91_adc_active_scan_mask_to_reg(struct iio_dev *indio_dev)
 	return mask & GENMASK(st->soc_info.platform->nr_channels, 0);
 }
 
+static void at91_adc_cor(struct at91_adc_state *st,
+			 struct iio_chan_spec const *chan)
+{
+	u32 cor, cur_cor;
+
+	cor = BIT(chan->channel) | BIT(chan->channel2);
+
+	cur_cor = at91_adc_readl(st, COR);
+	cor <<= st->soc_info.platform->layout->COR_diff_offset;
+	if (chan->differential)
+		at91_adc_writel(st, COR, cur_cor | cor);
+	else
+		at91_adc_writel(st, COR, cur_cor & ~cor);
+}
+
 static void at91_adc_irq_status(struct at91_adc_state *st, u32 *status,
 				u32 *eoc)
 {
@@ -1038,8 +1054,6 @@ static int at91_adc_buffer_prepare(struct iio_dev *indio_dev)
 			 indio_dev->num_channels) {
 		struct iio_chan_spec const *chan =
 					at91_adc_chan_get(indio_dev, bit);
-		u32 cor;
-
 		if (!chan)
 			continue;
 		/* these channel types cannot be handled by this trigger */
@@ -1047,16 +1061,7 @@ static int at91_adc_buffer_prepare(struct iio_dev *indio_dev)
 		    chan->type == IIO_PRESSURE)
 			continue;
 
-		cor = at91_adc_readl(st, COR);
-
-		if (chan->differential)
-			cor |= (BIT(chan->channel) | BIT(chan->channel2)) <<
-				AT91_SAMA5D2_COR_DIFF_OFFSET;
-		else
-			cor &= ~(BIT(chan->channel) <<
-			       AT91_SAMA5D2_COR_DIFF_OFFSET);
-
-		at91_adc_writel(st, COR, cor);
+		at91_adc_cor(st, chan);
 
 		at91_adc_writel(st, CHER, BIT(chan->channel));
 	}
@@ -1444,7 +1449,6 @@ static int at91_adc_read_info_raw(struct iio_dev *indio_dev,
 				  struct iio_chan_spec const *chan, int *val)
 {
 	struct at91_adc_state *st = iio_priv(indio_dev);
-	u32 cor = 0;
 	u16 tmp_val;
 	int ret;
 
@@ -1490,11 +1494,7 @@ static int at91_adc_read_info_raw(struct iio_dev *indio_dev,
 
 	st->chan = chan;
 
-	if (chan->differential)
-		cor = (BIT(chan->channel) | BIT(chan->channel2)) <<
-		      AT91_SAMA5D2_COR_DIFF_OFFSET;
-
-	at91_adc_writel(st, COR, cor);
+	at91_adc_cor(st, chan);
 	at91_adc_writel(st, CHER, BIT(chan->channel));
 	at91_adc_eoc_ena(st, chan->channel);
 	at91_adc_writel(st, CR, AT91_SAMA5D2_CR_START);