linux-kernel - [PATCH] counter: microchip-tcb-capture: Fix undefined counter channel state on probe

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Message-Id: <20250305-preset-capture-mode-microchip-tcb-capture-v1-1-632c95c6421e@kernel.org>
Date: Wed, 05 Mar 2025 19:01:19 +0900
From: William Breathitt Gray <wbg@...nel.org>
To: Csókás Bence <csokas.bence@...lan.hu>, 
 Kamel Bouhara <kamel.bouhara@...tlin.com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-iio@...r.kernel.org, 
 linux-kernel@...r.kernel.org, William Breathitt Gray <wbg@...nel.org>
Subject: [PATCH] counter: microchip-tcb-capture: Fix undefined counter
 channel state on probe

Hardware initialize of the timer counter channel does not occur on probe
thus leaving the Count in an undefined state until the first
function_write() callback is executed. Fix this by performing the proper
hardware initialization during probe.

Fixes: 106b104137fd ("counter: Add microchip TCB capture counter")
Reported-by: Csókás Bence <csokas.bence@...lan.hu>
Closes: https://lore.kernel.org/all/bfa70e78-3cc3-4295-820b-3925c26135cb@prolan.hu/
Signed-off-by: William Breathitt Gray <wbg@...nel.org>
---
This should fix the issue where a user needs to set the count function
before they can use the counter. I don't have this hardware in person,
so please test this patch and let me know whether it works for you.
---
 drivers/counter/microchip-tcb-capture.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/counter/microchip-tcb-capture.c b/drivers/counter/microchip-tcb-capture.c
index 2f096a5b973d18edf5de5a2b33f2f72571deefb7..c391ac38b990939c6764a9120a4bd03289f68469 100644
--- a/drivers/counter/microchip-tcb-capture.c
+++ b/drivers/counter/microchip-tcb-capture.c
@@ -368,6 +368,25 @@ static int mchp_tc_probe(struct platform_device *pdev)
 			channel);
 	}
 
+	/* Disable Quadrature Decoder and position measure */
+	ret = regmap_update_bits(regmap, ATMEL_TC_BMR, ATMEL_TC_QDEN | ATMEL_TC_POSEN, 0);
+	if (ret)
+		return ret;
+
+	/* Setup the period capture mode */
+	ret = regmap_update_bits(regmap, ATMEL_TC_REG(priv->channel[0], CMR),
+				 ATMEL_TC_WAVE | ATMEL_TC_ABETRG | ATMEL_TC_CMR_MASK |
+				 ATMEL_TC_TCCLKS,
+				 ATMEL_TC_CMR_MASK);
+	if (ret)
+		return ret;
+
+	/* Enable clock and trigger counter */
+	ret = regmap_write(regmap, ATMEL_TC_REG(priv->channel[0], CCR),
+			   ATMEL_TC_CLKEN | ATMEL_TC_SWTRG);
+	if (ret)
+		return ret;
+
 	priv->tc_cfg = tcb_config;
 	priv->regmap = regmap;
 	counter->name = dev_name(&pdev->dev);

---
base-commit: 8744dcd4fc7800de2eb9369410470bb2930d4c14
change-id: 20250305-preset-capture-mode-microchip-tcb-capture-fa31550ef594

Best regards,
-- 
William Breathitt Gray <wbg@...nel.org>