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From:   Alain Volmat <alain.volmat@foss.st.com>
To:     Andi Shyti <andi.shyti@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Alexandre Torgue <alexandre.torgue@foss.st.com>,
        Pierre-Yves MORDRET <pierre-yves.mordret@foss.st.com>,
        Alain Volmat <alain.volmat@foss.st.com>
CC:     <linux-i2c@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-stm32@st-md-mailman.stormreply.com>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>
Subject: [PATCH 1/7] i2c: stm32f7: perform most of irq job in threaded handler
Date:   Wed, 29 Nov 2023 13:59:10 +0100
Message-ID: <20231129125920.1702497-2-alain.volmat@foss.st.com>
In-Reply-To: <20231129125920.1702497-1-alain.volmat@foss.st.com>
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The irq handling is currently split between the irq handler
and the threaded irq handler.  Some of the handling (such as
dma related stuffs) done within the irq handler might sleep or
take some time leading to issues if the kernel is built with
realtime constraints.  In order to fix that, perform an overall
rework to perform most of the job within the threaded handler
and only keep fifo access in the non threaded handler.

Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
---
 drivers/i2c/busses/i2c-stm32f7.c | 126 ++++++++++++++-----------------
 1 file changed, 56 insertions(+), 70 deletions(-)

diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
index 983509936727..34dcc370e615 100644
--- a/drivers/i2c/busses/i2c-stm32f7.c
+++ b/drivers/i2c/busses/i2c-stm32f7.c
@@ -1497,17 +1497,11 @@ static irqreturn_t stm32f7_i2c_slave_isr_event(struct stm32f7_i2c_dev *i2c_dev)
 static irqreturn_t stm32f7_i2c_isr_event(int irq, void *data)
 {
 	struct stm32f7_i2c_dev *i2c_dev = data;
-	struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
-	struct stm32_i2c_dma *dma = i2c_dev->dma;
-	void __iomem *base = i2c_dev->base;
-	u32 status, mask;
-	int ret = IRQ_HANDLED;
+	u32 status;
 
-	/* Check if the interrupt if for a slave device */
-	if (!i2c_dev->master_mode) {
-		ret = stm32f7_i2c_slave_isr_event(i2c_dev);
-		return ret;
-	}
+	/* Check if the interrupt is for a slave device */
+	if (!i2c_dev->master_mode)
+		return IRQ_WAKE_THREAD;
 
 	status = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR);
 
@@ -1519,6 +1513,29 @@ static irqreturn_t stm32f7_i2c_isr_event(int irq, void *data)
 	if (status & STM32F7_I2C_ISR_RXNE)
 		stm32f7_i2c_read_rx_data(i2c_dev);
 
+	/* Wake up the thread if other flags are raised */
+	if (status &
+	    (STM32F7_I2C_ISR_NACKF | STM32F7_I2C_ISR_STOPF |
+	     STM32F7_I2C_ISR_TC | STM32F7_I2C_ISR_TCR))
+		return IRQ_WAKE_THREAD;
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t stm32f7_i2c_isr_event_thread(int irq, void *data)
+{
+	struct stm32f7_i2c_dev *i2c_dev = data;
+	struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
+	struct stm32_i2c_dma *dma = i2c_dev->dma;
+	void __iomem *base = i2c_dev->base;
+	u32 status, mask;
+	int ret;
+
+	if (!i2c_dev->master_mode)
+		return stm32f7_i2c_slave_isr_event(i2c_dev);
+
+	status = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR);
+
 	/* NACK received */
 	if (status & STM32F7_I2C_ISR_NACKF) {
 		dev_dbg(i2c_dev->dev, "<%s>: Receive NACK (addr %x)\n",
@@ -1531,33 +1548,28 @@ static irqreturn_t stm32f7_i2c_isr_event(int irq, void *data)
 		f7_msg->result = -ENXIO;
 	}
 
-	/* STOP detection flag */
-	if (status & STM32F7_I2C_ISR_STOPF) {
-		/* Disable interrupts */
-		if (stm32f7_i2c_is_slave_registered(i2c_dev))
-			mask = STM32F7_I2C_XFER_IRQ_MASK;
+	if (status & STM32F7_I2C_ISR_TCR) {
+		if (f7_msg->smbus)
+			stm32f7_i2c_smbus_reload(i2c_dev);
 		else
-			mask = STM32F7_I2C_ALL_IRQ_MASK;
-		stm32f7_i2c_disable_irq(i2c_dev, mask);
-
-		/* Clear STOP flag */
-		writel_relaxed(STM32F7_I2C_ICR_STOPCF, base + STM32F7_I2C_ICR);
-
-		if (i2c_dev->use_dma && !f7_msg->result) {
-			ret = IRQ_WAKE_THREAD;
-		} else {
-			i2c_dev->master_mode = false;
-			complete(&i2c_dev->complete);
-		}
+			stm32f7_i2c_reload(i2c_dev);
 	}
 
 	/* Transfer complete */
 	if (status & STM32F7_I2C_ISR_TC) {
+		/* Wait for dma transfer completion before sending next message */
+		if (i2c_dev->use_dma && !f7_msg->result) {
+			ret = wait_for_completion_timeout(&i2c_dev->dma->dma_complete, HZ);
+			if (!ret) {
+				dev_dbg(i2c_dev->dev, "<%s>: Timed out\n", __func__);
+				stm32f7_i2c_disable_dma_req(i2c_dev);
+				dmaengine_terminate_async(dma->chan_using);
+				f7_msg->result = -ETIMEDOUT;
+			}
+		}
 		if (f7_msg->stop) {
 			mask = STM32F7_I2C_CR2_STOP;
 			stm32f7_i2c_set_bits(base + STM32F7_I2C_CR2, mask);
-		} else if (i2c_dev->use_dma && !f7_msg->result) {
-			ret = IRQ_WAKE_THREAD;
 		} else if (f7_msg->smbus) {
 			stm32f7_i2c_smbus_rep_start(i2c_dev);
 		} else {
@@ -1567,47 +1579,18 @@ static irqreturn_t stm32f7_i2c_isr_event(int irq, void *data)
 		}
 	}
 
-	if (status & STM32F7_I2C_ISR_TCR) {
-		if (f7_msg->smbus)
-			stm32f7_i2c_smbus_reload(i2c_dev);
+	/* STOP detection flag */
+	if (status & STM32F7_I2C_ISR_STOPF) {
+		/* Disable interrupts */
+		if (stm32f7_i2c_is_slave_registered(i2c_dev))
+			mask = STM32F7_I2C_XFER_IRQ_MASK;
 		else
-			stm32f7_i2c_reload(i2c_dev);
-	}
-
-	return ret;
-}
-
-static irqreturn_t stm32f7_i2c_isr_event_thread(int irq, void *data)
-{
-	struct stm32f7_i2c_dev *i2c_dev = data;
-	struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
-	struct stm32_i2c_dma *dma = i2c_dev->dma;
-	u32 status;
-	int ret;
-
-	/*
-	 * Wait for dma transfer completion before sending next message or
-	 * notity the end of xfer to the client
-	 */
-	ret = wait_for_completion_timeout(&i2c_dev->dma->dma_complete, HZ);
-	if (!ret) {
-		dev_dbg(i2c_dev->dev, "<%s>: Timed out\n", __func__);
-		stm32f7_i2c_disable_dma_req(i2c_dev);
-		dmaengine_terminate_async(dma->chan_using);
-		f7_msg->result = -ETIMEDOUT;
-	}
+			mask = STM32F7_I2C_ALL_IRQ_MASK;
+		stm32f7_i2c_disable_irq(i2c_dev, mask);
 
-	status = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR);
+		/* Clear STOP flag */
+		writel_relaxed(STM32F7_I2C_ICR_STOPCF, base + STM32F7_I2C_ICR);
 
-	if (status & STM32F7_I2C_ISR_TC) {
-		if (f7_msg->smbus) {
-			stm32f7_i2c_smbus_rep_start(i2c_dev);
-		} else {
-			i2c_dev->msg_id++;
-			i2c_dev->msg++;
-			stm32f7_i2c_xfer_msg(i2c_dev, i2c_dev->msg);
-		}
-	} else {
 		i2c_dev->master_mode = false;
 		complete(&i2c_dev->complete);
 	}
@@ -1615,7 +1598,7 @@ static irqreturn_t stm32f7_i2c_isr_event_thread(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
-static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
+static irqreturn_t stm32f7_i2c_isr_error_thread(int irq, void *data)
 {
 	struct stm32f7_i2c_dev *i2c_dev = data;
 	struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
@@ -2205,8 +2188,11 @@ static int stm32f7_i2c_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	ret = devm_request_irq(&pdev->dev, irq_error, stm32f7_i2c_isr_error, 0,
-			       pdev->name, i2c_dev);
+	ret = devm_request_threaded_irq(&pdev->dev, irq_error,
+					NULL,
+					stm32f7_i2c_isr_error_thread,
+					IRQF_ONESHOT,
+					pdev->name, i2c_dev);
 	if (ret) {
 		dev_err(&pdev->dev, "Failed to request irq error %i\n",
 			irq_error);
-- 
2.25.1