linux-kernel - [PATCH v2 1/2] iio: dac: adi-axi-dac: fix bus read

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Message-Id: <20250409-ad3552r-fix-bus-read-v2-1-34d3b21e8ca0@baylibre.com>
Date: Wed, 09 Apr 2025 11:16:54 +0200
From: Angelo Dureghello <adureghello@...libre.com>
To: Nuno Sa <nuno.sa@...log.com>, Lars-Peter Clausen <lars@...afoo.de>, 
 Michael Hennerich <Michael.Hennerich@...log.com>, 
 Jonathan Cameron <jic23@...nel.org>, David Lechner <dlechner@...libre.com>, 
 Andy Shevchenko <andy@...nel.org>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
 Angelo Dureghello <adureghello@...libre.com>
Subject: [PATCH v2 1/2] iio: dac: adi-axi-dac: fix bus read

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

Fix bus read function.

Testing the driver, on a random basis, wrong reads was detected, mainly
by a wrong DAC chip ID read at first boot.
Before reading the expected value from the AXI regmap, need always to
wait for busy flag to be cleared.

Fixes: e61d7178429a ("iio: dac: adi-axi-dac: extend features")
Signed-off-by: Angelo Dureghello <adureghello@...libre.com>
---
 drivers/iio/dac/adi-axi-dac.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/iio/dac/adi-axi-dac.c b/drivers/iio/dac/adi-axi-dac.c
index 8ed5ad1fa24cef649056bc5f4ca80abbf28b9323..5ee077c58d7f9730aec8a9c9dff5b84108b3a47e 100644
--- a/drivers/iio/dac/adi-axi-dac.c
+++ b/drivers/iio/dac/adi-axi-dac.c
@@ -760,6 +760,7 @@ static int axi_dac_bus_reg_read(struct iio_backend *back, u32 reg, u32 *val,
 {
 	struct axi_dac_state *st = iio_backend_get_priv(back);
 	int ret;
+	u32 ival;
 
 	guard(mutex)(&st->lock);
 
@@ -772,6 +773,13 @@ static int axi_dac_bus_reg_read(struct iio_backend *back, u32 reg, u32 *val,
 	if (ret)
 		return ret;
 
+	ret = regmap_read_poll_timeout(st->regmap,
+				AXI_DAC_UI_STATUS_REG, ival,
+				FIELD_GET(AXI_DAC_UI_STATUS_IF_BUSY, ival) == 0,
+				10, 100 * KILO);
+	if (ret)
+		return ret;
+
 	return regmap_read(st->regmap, AXI_DAC_CUSTOM_RD_REG, val);
 }
 

-- 
2.49.0