[PATCH 5/7] iio: adc: stm32: add optional dma support

From: Fabrice Gasnier <fabrice.gasnier@st.com>
To: <jic23@kernel.org>, <linux@armlinux.org.uk>, <robh+dt@kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Cc: <linux-iio@vger.kernel.org>, <mark.rutland@arm.com>,
	<mcoquelin.stm32@gmail.com>, <alexandre.torgue@st.com>,
	<lars@metafoo.de>, <knaack.h@gmx.de>, <pmeerw@pmeerw.net>,
	<fabrice.gasnier@st.com>, <benjamin.gaignard@linaro.org>,
	<benjamin.gaignard@st.com>
Subject: [PATCH 5/7] iio: adc: stm32: add optional dma support
Date: Thu, 19 Jan 2017 14:34:12 +0100	[thread overview]
Message-ID: <1484832854-6314-6-git-send-email-fabrice.gasnier@st.com> (raw)
In-Reply-To: <1484832854-6314-1-git-send-email-fabrice.gasnier@st.com>

Add optional DMA support to STM32 ADC.
Use dma cyclic mode with at least two periods.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
---
 drivers/iio/adc/Kconfig          |   2 +
 drivers/iio/adc/stm32-adc-core.c |   1 +
 drivers/iio/adc/stm32-adc-core.h |   2 +
 drivers/iio/adc/stm32-adc.c      | 209 ++++++++++++++++++++++++++++++++++++---
 4 files changed, 202 insertions(+), 12 deletions(-)

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 9a7b090..2a2ef78 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -444,12 +444,14 @@ config ROCKCHIP_SARADC
 config STM32_ADC_CORE
 	tristate "STMicroelectronics STM32 adc core"
 	depends on ARCH_STM32 || COMPILE_TEST
+	depends on HAS_DMA
 	depends on OF
 	depends on REGULATOR
 	select IIO_BUFFER
 	select MFD_STM32_TIMERS
 	select IIO_STM32_TIMER_TRIGGER
 	select IIO_TRIGGERED_BUFFER
+	select IRQ_WORK
 	help
 	  Select this option to enable the core driver for STMicroelectronics
 	  STM32 analog-to-digital converter (ADC).
diff --git a/drivers/iio/adc/stm32-adc-core.c b/drivers/iio/adc/stm32-adc-core.c
index 4214b0c..22b7c93 100644
--- a/drivers/iio/adc/stm32-adc-core.c
+++ b/drivers/iio/adc/stm32-adc-core.c
@@ -201,6 +201,7 @@ static int stm32_adc_probe(struct platform_device *pdev)
 	priv->common.base = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(priv->common.base))
 		return PTR_ERR(priv->common.base);
+	priv->common.phys_base = res->start;
 
 	priv->vref = devm_regulator_get(&pdev->dev, "vref");
 	if (IS_ERR(priv->vref)) {
diff --git a/drivers/iio/adc/stm32-adc-core.h b/drivers/iio/adc/stm32-adc-core.h
index 081fa5f..2ec7abb 100644
--- a/drivers/iio/adc/stm32-adc-core.h
+++ b/drivers/iio/adc/stm32-adc-core.h
@@ -42,10 +42,12 @@
 /**
  * struct stm32_adc_common - stm32 ADC driver common data (for all instances)
  * @base:		control registers base cpu addr
+ * @phys_base:		control registers base physical addr
  * @vref_mv:		vref voltage (mv)
  */
 struct stm32_adc_common {
 	void __iomem			*base;
+	phys_addr_t			phys_base;
 	int				vref_mv;
 };
 
diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 9753c39..3439f4c 100644
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -21,6 +21,8 @@
 
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/dma-mapping.h>
+#include <linux/dmaengine.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/buffer.h>
 #include <linux/iio/timer/stm32-timer-trigger.h>
@@ -29,6 +31,7 @@
 #include <linux/iio/triggered_buffer.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
+#include <linux/irq_work.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/of.h>
@@ -69,6 +72,8 @@
 #define STM32F4_EXTSEL_SHIFT		24
 #define STM32F4_EXTSEL_MASK		GENMASK(27, 24)
 #define STM32F4_EOCS			BIT(10)
+#define STM32F4_DDS			BIT(9)
+#define STM32F4_DMA			BIT(8)
 #define STM32F4_ADON			BIT(0)
 
 /* STM32F4_ADC_SQR1 - bit fields */
@@ -165,6 +170,11 @@ struct stm32_adc_trig_info {
  * @bufi:		data buffer index
  * @num_conv:		expected number of scan conversions
  * @exten:		external trigger config (enable/polarity)
+ * @work:		irq work used to call trigger poll routine
+ * @dma_chan:		dma channel
+ * @rx_buf:		dma rx buffer cpu address
+ * @rx_dma_buf:		dma rx buffer bus address
+ * @rx_buf_sz:		dma rx buffer size
  */
 struct stm32_adc {
 	struct stm32_adc_common	*common;
@@ -177,6 +187,11 @@ struct stm32_adc {
 	int			bufi;
 	int			num_conv;
 	enum stm32_adc_exten	exten;
+	struct irq_work		work;
+	struct dma_chan		*dma_chan;
+	u8			*rx_buf;
+	dma_addr_t		rx_dma_buf;
+	int			rx_buf_sz;
 };
 
 /**
@@ -332,10 +347,20 @@ static void stm32_adc_conv_irq_disable(struct stm32_adc *adc)
 /**
  * stm32_adc_start_conv() - Start conversions for regular channels.
  * @adc: stm32 adc instance
+ *
+ * Start conversions for regular channels.
+ * Also take care of normal or DMA mode. DMA is used in circular mode for
+ * regular conversions, in IIO buffer modes. Rely on rx_buf as raw
+ * read doesn't use dma, but direct DR read.
  */
 static void stm32_adc_start_conv(struct stm32_adc *adc)
 {
 	stm32_adc_set_bits(adc, STM32F4_ADC_CR1, STM32F4_SCAN);
+
+	if (adc->rx_buf)
+		stm32_adc_set_bits(adc, STM32F4_ADC_CR2,
+				   STM32F4_DMA | STM32F4_DDS);
+
 	stm32_adc_set_bits(adc, STM32F4_ADC_CR2, STM32F4_EOCS | STM32F4_ADON);
 
 	/* Wait for Power-up time (tSTAB from datasheet) */
@@ -353,6 +378,10 @@ static void stm32_adc_stop_conv(struct stm32_adc *adc)
 
 	stm32_adc_clr_bits(adc, STM32F4_ADC_CR1, STM32F4_SCAN);
 	stm32_adc_clr_bits(adc, STM32F4_ADC_CR2, STM32F4_ADON);
+
+	if (adc->rx_buf)
+		stm32_adc_clr_bits(adc, STM32F4_ADC_CR2,
+				   STM32F4_DMA | STM32F4_DDS);
 }
 
 /**
@@ -689,19 +718,138 @@ static int stm32_adc_debugfs_reg_access(struct iio_dev *indio_dev,
 	.driver_module = THIS_MODULE,
 };
 
+static int stm32_adc_dma_residue(struct stm32_adc *adc)
+{
+	struct dma_tx_state state;
+	enum dma_status status;
+
+	if (!adc->rx_buf)
+		return 0;
+
+	status = dmaengine_tx_status(adc->dma_chan,
+				     adc->dma_chan->cookie,
+				     &state);
+	if (status == DMA_IN_PROGRESS) {
+		/* Residue is size in bytes from end of buffer */
+		int i = adc->rx_buf_sz - state.residue;
+		int size;
+
+		/* Return available bytes */
+		if (i >= adc->bufi)
+			size = i - adc->bufi;
+		else
+			size = adc->rx_buf_sz - adc->bufi + i;
+
+		return size;
+	}
+
+	return 0;
+}
+
+static void stm32_adc_dma_irq_work(struct irq_work *work)
+{
+	struct stm32_adc *adc = container_of(work, struct stm32_adc, work);
+	struct iio_dev *indio_dev = iio_priv_to_dev(adc);
+
+	/**
+	 * iio_trigger_poll calls generic_handle_irq(). So, it requires hard
+	 * irq context, and cannot be called directly from dma callback,
+	 * dma cb has to schedule this work instead.
+	 */
+	iio_trigger_poll(indio_dev->trig);
+}
+
+static void stm32_adc_dma_buffer_done(void *data)
+{
+	struct stm32_adc *adc = data;
+
+	/* invoques iio_trigger_poll() from hard irq context */
+	irq_work_queue(&adc->work);
+}
+
 static int stm32_adc_buffer_preenable(struct iio_dev *indio_dev)
 {
 	struct stm32_adc *adc = iio_priv(indio_dev);
+	struct dma_async_tx_descriptor *desc;
+	struct dma_slave_config config;
+	dma_cookie_t cookie;
+	int ret, size, watermark;
 
 	/* Reset adc buffer index */
 	adc->bufi = 0;
 
-	/* Allocate adc buffer */
-	adc->buffer = kzalloc(indio_dev->scan_bytes, GFP_KERNEL);
-	if (!adc->buffer)
+	if (!adc->dma_chan) {
+		/* Allocate adc buffer */
+		adc->buffer = kzalloc(indio_dev->scan_bytes, GFP_KERNEL);
+		if (!adc->buffer)
+			return -ENOMEM;
+
+		return 0;
+	}
+
+	/*
+	 * Allocate at least twice the buffer size for dma cyclic transfers, so
+	 * we can work with at least two dma periods. There should be :
+	 * - always one buffer (period) dma is working on
+	 * - one buffer (period) driver can push with iio_trigger_poll().
+	 */
+	size = indio_dev->buffer->bytes_per_datum * indio_dev->buffer->length;
+	size = max(indio_dev->scan_bytes * 2, size);
+
+	adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev,
+					 PAGE_ALIGN(size), &adc->rx_dma_buf,
+					 GFP_KERNEL);
+	if (!adc->rx_buf)
 		return -ENOMEM;
+	adc->rx_buf_sz = size;
+	watermark = indio_dev->buffer->bytes_per_datum
+		* indio_dev->buffer->watermark;
+	watermark = max(indio_dev->scan_bytes, watermark);
+	watermark = rounddown(watermark, indio_dev->scan_bytes);
+
+	dev_dbg(&indio_dev->dev, "%s size=%d watermark=%d\n", __func__, size,
+		watermark);
+
+	/* Configure DMA channel to read data register */
+	memset(&config, 0, sizeof(config));
+	config.src_addr = (dma_addr_t)adc->common->phys_base;
+	config.src_addr += adc->offset + STM32F4_ADC_DR;
+	config.src_addr_width = DMA_SLAVE_BUSWIDTH_2_BYTES;
+
+	ret = dmaengine_slave_config(adc->dma_chan, &config);
+	if (ret)
+		goto config_err;
+
+	/* Prepare a DMA cyclic transaction */
+	desc = dmaengine_prep_dma_cyclic(adc->dma_chan,
+					 adc->rx_dma_buf,
+					 size, watermark,
+					 DMA_DEV_TO_MEM,
+					 DMA_PREP_INTERRUPT);
+	if (!desc) {
+		ret = -ENODEV;
+		goto config_err;
+	}
+
+	desc->callback = stm32_adc_dma_buffer_done;
+	desc->callback_param = adc;
+
+	cookie = dmaengine_submit(desc);
+	if (dma_submit_error(cookie)) {
+		ret = dma_submit_error(cookie);
+		goto config_err;
+	}
+
+	/* Issue pending DMA requests */
+	dma_async_issue_pending(adc->dma_chan);
 
 	return 0;
+
+config_err:
+	dma_free_coherent(adc->dma_chan->device->dev, PAGE_ALIGN(size),
+			  adc->rx_buf, adc->rx_dma_buf);
+
+	return ret;
 }
 
 static int stm32_adc_buffer_postenable(struct iio_dev *indio_dev)
@@ -719,7 +867,8 @@ static int stm32_adc_buffer_postenable(struct iio_dev *indio_dev)
 	if (ret < 0)
 		return ret;
 
-	stm32_adc_conv_irq_enable(adc);
+	if (!adc->dma_chan)
+		stm32_adc_conv_irq_enable(adc);
 	stm32_adc_start_conv(adc);
 
 	return 0;
@@ -731,7 +880,8 @@ static int stm32_adc_buffer_predisable(struct iio_dev *indio_dev)
 	int ret;
 
 	stm32_adc_stop_conv(adc);
-	stm32_adc_conv_irq_disable(adc);
+	if (!adc->dma_chan)
+		stm32_adc_conv_irq_disable(adc);
 
 	ret = iio_triggered_buffer_predisable(indio_dev);
 	if (ret < 0)
@@ -748,7 +898,16 @@ static int stm32_adc_buffer_postdisable(struct iio_dev *indio_dev)
 {
 	struct stm32_adc *adc = iio_priv(indio_dev);
 
-	kfree(adc->buffer);
+	if (!adc->dma_chan) {
+		kfree(adc->buffer);
+	} else {
+		dmaengine_terminate_all(adc->dma_chan);
+		irq_work_sync(&adc->work);
+		dma_free_coherent(adc->dma_chan->device->dev,
+				  PAGE_ALIGN(adc->rx_buf_sz),
+				  adc->rx_buf, adc->rx_dma_buf);
+		adc->rx_buf = NULL;
+	}
 	adc->buffer = NULL;
 
 	return 0;
@@ -769,15 +928,31 @@ static irqreturn_t stm32_adc_trigger_handler(int irq, void *p)
 
 	dev_dbg(&indio_dev->dev, "%s bufi=%d\n", __func__, adc->bufi);
 
-	/* reset buffer index */
-	adc->bufi = 0;
-	iio_push_to_buffers_with_timestamp(indio_dev, adc->buffer,
-					   pf->timestamp);
+	if (!adc->dma_chan) {
+		/* reset buffer index */
+		adc->bufi = 0;
+		iio_push_to_buffers_with_timestamp(indio_dev, adc->buffer,
+						   pf->timestamp);
+	} else {
+		int residue = stm32_adc_dma_residue(adc);
+
+		while (residue >= indio_dev->scan_bytes) {
+			adc->buffer = (u16 *)&adc->rx_buf[adc->bufi];
+			iio_push_to_buffers_with_timestamp(indio_dev,
+							   adc->buffer,
+							   pf->timestamp);
+			residue -= indio_dev->scan_bytes;
+			adc->bufi += indio_dev->scan_bytes;
+			if (adc->bufi >= adc->rx_buf_sz)
+				adc->bufi = 0;
+		}
+	}
 
 	iio_trigger_notify_done(indio_dev->trig);
 
 	/* re-enable eoc irq */
-	stm32_adc_conv_irq_enable(adc);
+	if (!adc->dma_chan)
+		stm32_adc_conv_irq_enable(adc);
 
 	return IRQ_HANDLED;
 }
@@ -910,13 +1085,17 @@ static int stm32_adc_probe(struct platform_device *pdev)
 	if (ret < 0)
 		goto err_clk_disable;
 
+	adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx");
+	if (adc->dma_chan)
+		init_irq_work(&adc->work, stm32_adc_dma_irq_work);
+
 	ret = iio_triggered_buffer_setup(indio_dev,
 					 &iio_pollfunc_store_time,
 					 &stm32_adc_trigger_handler,
 					 &stm32_adc_buffer_setup_ops);
 	if (ret) {
 		dev_err(&pdev->dev, "buffer setup failed\n");
-		goto err_clk_disable;
+		goto err_dma_disable;
 	}
 
 	ret = iio_device_register(indio_dev);
@@ -930,6 +1109,10 @@ static int stm32_adc_probe(struct platform_device *pdev)
 err_buffer_cleanup:
 	iio_triggered_buffer_cleanup(indio_dev);
 
+err_dma_disable:
+	if (adc->dma_chan)
+		dma_release_channel(adc->dma_chan);
+
 err_clk_disable:
 	clk_disable_unprepare(adc->clk);
 
@@ -943,6 +1126,8 @@ static int stm32_adc_remove(struct platform_device *pdev)
 
 	iio_device_unregister(indio_dev);
 	iio_triggered_buffer_cleanup(indio_dev);
+	if (adc->dma_chan)
+		dma_release_channel(adc->dma_chan);
 	clk_disable_unprepare(adc->clk);
 
 	return 0;
-- 
1.9.1
