iio: adc: ad9361: Avoid clobbering MGC set gain when switching gain t…

…ables

This fixes unintentional resets to MAX gain when moving RX LO between
gain table coverage boundaries.
When switching gain tables only enforce set gain below max gain.
Otherwise avoid clobbering the current gain index.

Signed-off-by: Michael Hennerich <[email protected]>

drivers/iio/adc/ad9361.c

@@ -1173,7 +1173,7 @@ static int ad9361_load_gt(struct ad9361_rf_phy *phy, u64 freq, u32 dest)
 {
 	struct spi_device *spi = phy->spi;
 	u8 (*tab)[3];
-	u32 band, index_max, i, lna, lpf_tia_mask;
+	u32 band, index_max, i, lna, lpf_tia_mask, set_gain;
 
 	dev_dbg(&phy->spi->dev, "%s: frequency %llu", __func__, freq);
 
@@ -1192,10 +1192,19 @@ static int ad9361_load_gt(struct ad9361_rf_phy *phy, u64 freq, u32 dest)
 	ad9361_spi_writef(spi, REG_AGC_CONFIG_2,
 			  AGC_USE_FULL_GAIN_TABLE, !phy->pdata->split_gt);
 
-	ad9361_spi_write(spi, REG_MAX_LMT_FULL_GAIN, index_max - 1); // Max Full/LMT Gain Table Index
-	ad9361_spi_writef(spi, REG_RX1_MANUAL_LMT_FULL_GAIN,
-			  RX_FULL_TBL_IDX_MASK,  index_max - 1); // Rx1 Full/LMT Gain Index
-	ad9361_spi_write(spi, REG_RX2_MANUAL_LMT_FULL_GAIN, index_max - 1); // Rx2 Full/LMT Gain Index
+	ad9361_spi_write(spi, REG_MAX_LMT_FULL_GAIN, index_max - 1); /* Max Full/LMT Gain Table Index */
+
+	set_gain = ad9361_spi_readf(spi, REG_RX1_MANUAL_LMT_FULL_GAIN,
+				    RX_FULL_TBL_IDX_MASK);
+	if (set_gain > (index_max - 1))
+		ad9361_spi_writef(spi, REG_RX1_MANUAL_LMT_FULL_GAIN,
+				  RX_FULL_TBL_IDX_MASK,  index_max - 1); /* Rx1 Full/LMT Gain Index */
+
+	set_gain = ad9361_spi_readf(spi, REG_RX2_MANUAL_LMT_FULL_GAIN,
+				    RX_FULL_TBL_IDX_MASK);
+	if (set_gain > (index_max - 1))
+		ad9361_spi_write(spi, REG_RX2_MANUAL_LMT_FULL_GAIN,
+				 index_max - 1); /* Rx2 Full/LMT Gain Index */
 
 	lna = phy->pdata->elna_ctrl.elna_in_gaintable_all_index_en ?
 		EXT_LNA_CTRL : 0;