linux-kernel - [PATCH 1/3] iio: adc: stm32: fix common clock rate

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Date:   Tue, 18 Jul 2017 14:35:30 +0200
From:   Fabrice Gasnier <fabrice.gasnier@...com>
To:     <jic23@...nel.org>, <robh+dt@...nel.org>
CC:     <linux@...linux.org.uk>, <mark.rutland@....com>,
        <mcoquelin.stm32@...il.com>, <alexandre.torgue@...com>,
        <lars@...afoo.de>, <knaack.h@....de>, <pmeerw@...erw.net>,
        <fabrice.gasnier@...com>, <benjamin.gaignard@...aro.org>,
        <benjamin.gaignard@...com>, <linux-iio@...r.kernel.org>,
        <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/3] iio: adc: stm32: fix common clock rate

Fixes commit 95e339b6e85d ("iio: adc: stm32: add support for STM32H7")

Fix common clock rate used then by stm32-adc sub-devices: take common
prescaler into account.
Fix ADC max clock rate on STM32H7 (fADC from datasheet)

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>
---
 drivers/iio/adc/stm32-adc-core.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/adc/stm32-adc-core.c b/drivers/iio/adc/stm32-adc-core.c
index e09233b..6096763 100644
--- a/drivers/iio/adc/stm32-adc-core.c
+++ b/drivers/iio/adc/stm32-adc-core.c
@@ -64,7 +64,7 @@
 #define STM32H7_CKMODE_MASK		GENMASK(17, 16)
 
 /* STM32 H7 maximum analog clock rate (from datasheet) */
-#define STM32H7_ADC_MAX_CLK_RATE	72000000
+#define STM32H7_ADC_MAX_CLK_RATE	36000000
 
 /**
  * stm32_adc_common_regs - stm32 common registers, compatible dependent data
@@ -148,14 +148,14 @@ static int stm32f4_adc_clk_sel(struct platform_device *pdev,
 		return -EINVAL;
 	}
 
-	priv->common.rate = rate;
+	priv->common.rate = rate / stm32f4_pclk_div[i];
 	val = readl_relaxed(priv->common.base + STM32F4_ADC_CCR);
 	val &= ~STM32F4_ADC_ADCPRE_MASK;
 	val |= i << STM32F4_ADC_ADCPRE_SHIFT;
 	writel_relaxed(val, priv->common.base + STM32F4_ADC_CCR);
 
 	dev_dbg(&pdev->dev, "Using analog clock source at %ld kHz\n",
-		rate / (stm32f4_pclk_div[i] * 1000));
+		priv->common.rate / 1000);
 
 	return 0;
 }
@@ -250,7 +250,7 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev,
 
 out:
 	/* rate used later by each ADC instance to control BOOST mode */
-	priv->common.rate = rate;
+	priv->common.rate = rate / div;
 
 	/* Set common clock mode and prescaler */
 	val = readl_relaxed(priv->common.base + STM32H7_ADC_CCR);
@@ -260,7 +260,7 @@ static int stm32h7_adc_clk_sel(struct platform_device *pdev,
 	writel_relaxed(val, priv->common.base + STM32H7_ADC_CCR);
 
 	dev_dbg(&pdev->dev, "Using %s clock/%d source at %ld kHz\n",
-		ckmode ? "bus" : "adc", div, rate / (div * 1000));
+		ckmode ? "bus" : "adc", div, priv->common.rate / 1000);
 
 	return 0;
 }
-- 
1.9.1