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From: Fabrice Gasnier <fabrice.gasnier@st.com>
To: <jic23@kernel.org>
Cc: <linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>, <mcoquelin.stm32@gmail.com>,
	<alexandre.torgue@st.com>, <fabrice.gasnier@st.com>,
	<linux-iio@vger.kernel.org>, <lars@metafoo.de>, <knaack.h@gmx.de>,
	<pmeerw@pmeerw.net>, <linux-stm32@st-md-mailman.stormreply.com>,
	<arnaud.pouliquen@st.com>, <olivier.moysan@st.com>
Subject: [PATCH 1/8] iio: adc: stm32-dfsdm: make spi_master_freq more accurate
Date: Wed, 6 Mar 2019 09:55:17 +0100	[thread overview]
Message-ID: <1551862524-25098-2-git-send-email-fabrice.gasnier@st.com> (raw)
In-Reply-To: <1551862524-25098-1-git-send-email-fabrice.gasnier@st.com>

When SPI clock isn't accurate, 'spi_master_freq' is filled in with
expected frequency. Use computed value instead:
- e.g. source clock / (CKOUTDIV + 1)
Also, current divider may be set to value that makes CKOUT to exceed
spi-max-frequency. Rather use lower value (e.g. round up divider when
ckout isn't accurate).

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
---
 drivers/iio/adc/stm32-dfsdm-core.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/stm32-dfsdm-core.c b/drivers/iio/adc/stm32-dfsdm-core.c
index bf089f5..65b7556 100644
--- a/drivers/iio/adc/stm32-dfsdm-core.c
+++ b/drivers/iio/adc/stm32-dfsdm-core.c
@@ -243,13 +243,18 @@ static int stm32_dfsdm_parse_of(struct platform_device *pdev,
 		return 0;
 	}
 
-	priv->spi_clk_out_div = div_u64_rem(clk_freq, spi_freq, &rem) - 1;
+	priv->spi_clk_out_div = div_u64_rem(clk_freq, spi_freq, &rem);
+
+	/* round up divider when clkout isn't accurate (e.g. !rem) */
+	if (priv->spi_clk_out_div && !rem)
+		priv->spi_clk_out_div--;
+
 	if (!priv->spi_clk_out_div) {
 		/* spi_clk_out_div == 0 means ckout is OFF */
 		dev_err(&pdev->dev, "spi-max-frequency not achievable\n");
 		return -EINVAL;
 	}
-	priv->dfsdm.spi_master_freq = spi_freq;
+	priv->dfsdm.spi_master_freq = clk_freq / (priv->spi_clk_out_div + 1);
 
 	if (rem) {
 		dev_warn(&pdev->dev, "SPI clock not accurate\n");
-- 
2.7.4


WARNING: multiple messages have this Message-ID (diff)
From: Fabrice Gasnier <fabrice.gasnier@st.com>
To: <jic23@kernel.org>
Cc: lars@metafoo.de, olivier.moysan@st.com, alexandre.torgue@st.com,
	linux-iio@vger.kernel.org, pmeerw@pmeerw.net,
	arnaud.pouliquen@st.com, linux-kernel@vger.kernel.org,
	mcoquelin.stm32@gmail.com, knaack.h@gmx.de,
	fabrice.gasnier@st.com, linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/8] iio: adc: stm32-dfsdm: make spi_master_freq more accurate
Date: Wed, 6 Mar 2019 09:55:17 +0100	[thread overview]
Message-ID: <1551862524-25098-2-git-send-email-fabrice.gasnier@st.com> (raw)
In-Reply-To: <1551862524-25098-1-git-send-email-fabrice.gasnier@st.com>

When SPI clock isn't accurate, 'spi_master_freq' is filled in with
expected frequency. Use computed value instead:
- e.g. source clock / (CKOUTDIV + 1)
Also, current divider may be set to value that makes CKOUT to exceed
spi-max-frequency. Rather use lower value (e.g. round up divider when
ckout isn't accurate).

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
---
 drivers/iio/adc/stm32-dfsdm-core.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/stm32-dfsdm-core.c b/drivers/iio/adc/stm32-dfsdm-core.c
index bf089f5..65b7556 100644
--- a/drivers/iio/adc/stm32-dfsdm-core.c
+++ b/drivers/iio/adc/stm32-dfsdm-core.c
@@ -243,13 +243,18 @@ static int stm32_dfsdm_parse_of(struct platform_device *pdev,
 		return 0;
 	}
 
-	priv->spi_clk_out_div = div_u64_rem(clk_freq, spi_freq, &rem) - 1;
+	priv->spi_clk_out_div = div_u64_rem(clk_freq, spi_freq, &rem);
+
+	/* round up divider when clkout isn't accurate (e.g. !rem) */
+	if (priv->spi_clk_out_div && !rem)
+		priv->spi_clk_out_div--;
+
 	if (!priv->spi_clk_out_div) {
 		/* spi_clk_out_div == 0 means ckout is OFF */
 		dev_err(&pdev->dev, "spi-max-frequency not achievable\n");
 		return -EINVAL;
 	}
-	priv->dfsdm.spi_master_freq = spi_freq;
+	priv->dfsdm.spi_master_freq = clk_freq / (priv->spi_clk_out_div + 1);
 
 	if (rem) {
 		dev_warn(&pdev->dev, "SPI clock not accurate\n");
-- 
2.7.4


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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2019-03-06  8:56 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-06  8:55 [PATCH 0/8] iio: adc: stm32-dfsdm: add buffer modes Fabrice Gasnier
2019-03-06  8:55 ` Fabrice Gasnier
2019-03-06  8:55 ` Fabrice Gasnier [this message]
2019-03-06  8:55   ` [PATCH 1/8] iio: adc: stm32-dfsdm: make spi_master_freq more accurate Fabrice Gasnier
2019-03-10 10:09   ` Jonathan Cameron
2019-03-10 10:09     ` Jonathan Cameron
2019-03-21 13:41     ` Fabrice Gasnier
2019-03-21 13:41       ` Fabrice Gasnier
2019-03-06  8:55 ` [PATCH 2/8] iio: adc: stm32-dfsdm: continuous mode depends on current mode Fabrice Gasnier
2019-03-06  8:55   ` Fabrice Gasnier
2019-03-06  8:55 ` [PATCH 3/8] iio: adc: stm32-dfsdm: move dma enable from start_conv() to start_dma() Fabrice Gasnier
2019-03-06  8:55   ` Fabrice Gasnier
2019-03-06  8:55 ` [PATCH 4/8] iio: adc: stm32-dfsdm: move dma slave config to start routine Fabrice Gasnier
2019-03-06  8:55   ` Fabrice Gasnier
2019-03-06  8:55 ` [PATCH 5/8] iio: adc: stm32-dfsdm: enable hw consumer Fabrice Gasnier
2019-03-06  8:55   ` Fabrice Gasnier
2019-03-06  8:55 ` [PATCH 6/8] iio: adc: stm32-dfsdm: add support for scan mode Fabrice Gasnier
2019-03-06  8:55   ` Fabrice Gasnier
2019-03-06  8:55 ` [PATCH 7/8] iio: adc: stm32-dfsdm: add support for buffer modes Fabrice Gasnier
2019-03-06  8:55   ` Fabrice Gasnier
2019-03-10 10:21   ` Jonathan Cameron
2019-03-10 10:21     ` Jonathan Cameron
2019-03-15 18:01     ` Fabrice Gasnier
2019-03-15 18:01       ` Fabrice Gasnier
2019-03-16 14:10       ` Jonathan Cameron
2019-03-16 14:10         ` Jonathan Cameron
2019-03-21 13:41         ` Fabrice Gasnier
2019-03-21 13:41           ` Fabrice Gasnier
2019-03-06  8:55 ` [PATCH 8/8] iio: adc: stm32-dfsdm: claim direct mode for raw read and settings Fabrice Gasnier
2019-03-06  8:55   ` Fabrice Gasnier

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