linux-kernel - [PATCH v2] iio: adc: aspeed: Deassert reset in probe

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Message-Id: <20171031021203.18248-1-joel@jms.id.au>
Date:   Tue, 31 Oct 2017 12:42:03 +1030
From:   Joel Stanley <joel@....id.au>
To:     Jonathan Cameron <jic23@...nel.org>,
        Rick Altherr <raltherr@...gle.com>,
        Rob Herring <robh+dt@...nel.org>
Cc:     Philipp Zabel <philipp.zabel@...il.com>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] iio: adc: aspeed: Deassert reset in probe

The ASPEED SoC must deassert a reset in order to use the ADC peripheral.

The device tree bindings are updated to document the resets phandle, and
the example is updated to match what is expected for both the reset and
clock phandle. Note that the bindings should have always had the reset
controller, as the hardware is unusable without it.

Signed-off-by: Joel Stanley <joel@....id.au>
---
v2:
 - Ensure disabling path unwinds in opposite order as the enable path
 - Note that the bindings were incorrect without the reset phandle,
 and for the system to be usable we must update them. No one was
 (successfully) using these bindings/driver before without out of tree
 hacks in mach-aspeed, as it would not have worked.

 .../devicetree/bindings/iio/adc/aspeed_adc.txt     |  4 +++-
 drivers/iio/adc/aspeed_adc.c                       | 25 ++++++++++++++++------
 2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/aspeed_adc.txt b/Documentation/devicetree/bindings/iio/adc/aspeed_adc.txt
index 674e133b7cd7..034fc2ba100e 100644
--- a/Documentation/devicetree/bindings/iio/adc/aspeed_adc.txt
+++ b/Documentation/devicetree/bindings/iio/adc/aspeed_adc.txt
@@ -8,6 +8,7 @@ Required properties:
 - reg: memory window mapping address and length
 - clocks: Input clock used to derive the sample clock. Expected to be the
           SoC's APB clock.
+- resets: Reset controller phandle
 - #io-channel-cells: Must be set to <1> to indicate channels are selected
                      by index.
 
@@ -15,6 +16,7 @@ Example:
 	adc@...e9000 {
 		compatible = "aspeed,ast2400-adc";
 		reg = <0x1e6e9000 0xb0>;
-		clocks = <&clk_apb>;
+		clocks = <&syscon ASPEED_CLK_APB>;
+		resets = <&syscon ASPEED_RESET_ADC>;
 		#io-channel-cells = <1>;
 	};
diff --git a/drivers/iio/adc/aspeed_adc.c b/drivers/iio/adc/aspeed_adc.c
index 8a958d5f1905..327a49ba1991 100644
--- a/drivers/iio/adc/aspeed_adc.c
+++ b/drivers/iio/adc/aspeed_adc.c
@@ -17,6 +17,7 @@
 #include <linux/module.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
+#include <linux/reset.h>
 #include <linux/spinlock.h>
 #include <linux/types.h>
 
@@ -53,11 +54,12 @@ struct aspeed_adc_model_data {
 };
 
 struct aspeed_adc_data {
-	struct device	*dev;
-	void __iomem	*base;
-	spinlock_t	clk_lock;
-	struct clk_hw	*clk_prescaler;
-	struct clk_hw	*clk_scaler;
+	struct device		*dev;
+	void __iomem		*base;
+	spinlock_t		clk_lock;
+	struct clk_hw		*clk_prescaler;
+	struct clk_hw		*clk_scaler;
+	struct reset_control	*rst;
 };
 
 #define ASPEED_CHAN(_idx, _data_reg_addr) {			\
@@ -217,6 +219,15 @@ static int aspeed_adc_probe(struct platform_device *pdev)
 		goto scaler_error;
 	}
 
+	data->rst = devm_reset_control_get_exclusive(&pdev->dev, NULL);
+	if (IS_ERR(data->rst)) {
+		dev_err(&pdev->dev,
+			"invalid or missing reset controller device tree entry");
+		ret = PTR_ERR(data->rst);
+		goto reset_error;
+	}
+	reset_control_deassert(data->rst);
+
 	model_data = of_device_get_match_data(&pdev->dev);
 
 	if (model_data->wait_init_sequence) {
@@ -263,9 +274,10 @@ static int aspeed_adc_probe(struct platform_device *pdev)
 	writel(ASPEED_OPERATION_MODE_POWER_DOWN,
 		data->base + ASPEED_REG_ENGINE_CONTROL);
 	clk_disable_unprepare(data->clk_scaler->clk);
+reset_error:
+	reset_control_assert(data->rst);
 clk_enable_error:
 	clk_hw_unregister_divider(data->clk_scaler);
-
 scaler_error:
 	clk_hw_unregister_divider(data->clk_prescaler);
 	return ret;
@@ -280,6 +292,7 @@ static int aspeed_adc_remove(struct platform_device *pdev)
 	writel(ASPEED_OPERATION_MODE_POWER_DOWN,
 		data->base + ASPEED_REG_ENGINE_CONTROL);
 	clk_disable_unprepare(data->clk_scaler->clk);
+	reset_control_assert(data->rst);
 	clk_hw_unregister_divider(data->clk_scaler);
 	clk_hw_unregister_divider(data->clk_prescaler);
 
-- 
2.14.1