linux-kernel - [PATCH v3] staging: iio: ad5933: Correct settling cycles encoding per datasheet

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Message-ID: <20250420003000.842747-1-gshahrouzi@gmail.com>
Date: Sat, 19 Apr 2025 20:30:00 -0400
From: Gabriel Shahrouzi <gshahrouzi@...il.com>
To: gregkh@...uxfoundation.org,
	jic23@...nel.org,
	lars@...afoo.de,
	linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-staging@...ts.linux.dev,
	Michael.Hennerich@...log.com
Cc: gshahrouzi@...il.com,
	skhan@...uxfoundation.org,
	linux-kernel-mentees@...ts.linux.dev,
	stable@...r.kernel.org
Subject: [PATCH v3] staging: iio: ad5933: Correct settling cycles encoding per datasheet

Implement the settling cycles encoding as specified in the AD5933
datasheet, Table 13 ("Number of Settling Times Cycles Register"). The
previous logic did not correctly translate the user-requested effective
cycle count into the required 9-bit base + 2-bit multiplier format
(D10..D0) for values exceeding 511.

Clamp the user input for out_altvoltage0_settling_cycles to the
maximum effective value of 2044 cycles (511 * 4x multiplier).

Fixes: f94aa354d676 ("iio: impedance-analyzer: New driver for AD5933/4 Impedance Converter, Network Analyzer")
Cc: stable@...r.kernel.org
Signed-off-by: Gabriel Shahrouzi <gshahrouzi@...il.com>
---
Changes in v3:
	- Only include fix (remove refactoring which will be its own
	  separate patch).
Changes in v2:
        - Fix spacing in comment around '+'.
        - Define mask and values for settling cycle multipliers.
---
 drivers/staging/iio/impedance-analyzer/ad5933.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/iio/impedance-analyzer/ad5933.c b/drivers/staging/iio/impedance-analyzer/ad5933.c
index d5544fc2fe989..f8fcc10ea8150 100644
--- a/drivers/staging/iio/impedance-analyzer/ad5933.c
+++ b/drivers/staging/iio/impedance-analyzer/ad5933.c
@@ -411,7 +411,7 @@ static ssize_t ad5933_store(struct device *dev,
 		ret = ad5933_cmd(st, 0);
 		break;
 	case AD5933_OUT_SETTLING_CYCLES:
-		val = clamp(val, (u16)0, (u16)0x7FF);
+		val = clamp(val, (u16)0, (u16)0x7FC);
 		st->settling_cycles = val;
 
 		/* 2x, 4x handling, see datasheet */
-- 
2.43.0