linux-kernel - [PATCH v3] iio: adc: ad7606: fix serial register access

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Message-Id: <20250418-wip-bl-ad7606-fix-reg-access-v3-1-d5eeb440c738@baylibre.com>
Date: Fri, 18 Apr 2025 20:37:53 +0200
From: Angelo Dureghello <adureghello@...libre.com>
To: Lars-Peter Clausen <lars@...afoo.de>, 
 Michael Hennerich <Michael.Hennerich@...log.com>, 
 Jonathan Cameron <jic23@...nel.org>, David Lechner <dlechner@...libre.com>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Andy Shevchenko <andy@...nel.org>, Beniamin Bia <beniamin.bia@...log.com>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Angelo Dureghello <adureghello@...libre.com>
Subject: [PATCH v3] iio: adc: ad7606: fix serial register access

From: Angelo Dureghello <adureghello@...libre.com>

Fix register read/write routine as per datasheet.

When reading multiple consecutive registers, only the first one is read
properly. This is due to missing chip select deassert and assert again
between first and second 16bit transfer, as shown in the datasheet
AD7606C-16, rev 0, figure 110.

Fixes: f2a22e1e172f ("iio: adc: ad7606: Add support for software mode for ad7616")
Reviewed-by: David Lechner <dlechner@...libre.com>
Signed-off-by: Angelo Dureghello <adureghello@...libre.com>
---
Changes in v3:
- fix typo in commit descritpion.
- Link to v2: https://lore.kernel.org/r/20250418-wip-bl-ad7606-fix-reg-access-v2-1-8b1ade67e185@baylibre.com

Changes in v2:
- improve bug description.
- Link to v1: https://lore.kernel.org/r/20250417-wip-bl-ad7606-fix-reg-access-v1-1-0ce341f3cfc3@baylibre.com
---
 drivers/iio/adc/ad7606_spi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/adc/ad7606_spi.c b/drivers/iio/adc/ad7606_spi.c
index 997be483ebb93293481b922e13ece4edb47e940a..bd05357a542cf7234d5bb6b718829d6b720262cd 100644
--- a/drivers/iio/adc/ad7606_spi.c
+++ b/drivers/iio/adc/ad7606_spi.c
@@ -103,7 +103,7 @@ static int ad7606_spi_reg_read(struct ad7606_state *st, unsigned int addr)
 		{
 			.tx_buf = &st->d16[0],
 			.len = 2,
-			.cs_change = 0,
+			.cs_change = 1,
 		}, {
 			.rx_buf = &st->d16[1],
 			.len = 2,

---
base-commit: 8dc6b228d746b1a900bed28568defb2266fa4c43
change-id: 20250417-wip-bl-ad7606-fix-reg-access-729c21478d1f

Best regards,
-- 
Angelo Dureghello <adureghello@...libre.com>