uio: xilinx_ai_engine: Simulate the irq if no hw irq is available

Only when there's no hw irq available and the debugfs is enabled,
simulate the irq. This allows users to trigger the interrupt through
debugfs and helps debug, as some emulation platforms don't even
have the NPI interrupt connected.

Signed-off-by: Hyun Kwon <[email protected]>
Reviewed-by: Wendy Liang <[email protected]>
Signed-off-by: Michal Simek <[email protected]>

drivers/uio/Kconfig

@@ -179,6 +179,7 @@ config UIO_XILINX_APM
 
 config UIO_XILINX_AI_ENGINE
 	tristate "Xilinx AI Engine driver"
+	select IRQ_SIM
 	select UIO_DMEM_GENIRQ
 	help
 	  The driver for Xilinx AI Engine that utilizes the uio_dmem_genirq.

drivers/uio/uio_xilinx_ai_engine.c

@@ -7,6 +7,8 @@
  * Author: Hyun Woo Kwon <[email protected]>
  */
 
+#include <linux/debugfs.h>
+#include <linux/irq_sim.h>
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/of.h>
@@ -27,6 +29,102 @@ module_param_named(mem_size, xilinx_ai_engine_mem_size, uint, 0444);
 MODULE_PARM_DESC(mem_size,
 		 "Dynamic memory allocation size in bytes (default: 32 MB)");
 
+#ifdef CONFIG_DEBUG_FS
+
+static ssize_t xilinx_ai_engine_debugfs_write(struct file *f,
+					      const char __user *buf,
+					      size_t size, loff_t *pos)
+{
+	struct irq_sim *irq_sim = file_inode(f)->i_private;
+
+	irq_sim_fire(irq_sim, 1);
+
+	return size;
+}
+
+static const struct file_operations debugfs_ops = {
+	.owner = THIS_MODULE,
+	.write = xilinx_ai_engine_debugfs_write,
+};
+
+/**
+ * xilinx_ai_engine_debugfs_init - Initialize the debugfs for irq sim
+ * @pdev: platform device to simulate irq for
+ * @irq_sim: simualated irq
+ *
+ * Initialize the debugfs for irq simulation. This allows to generate
+ * the simulated interrupt from user.
+ *
+ * Return: 0 for success, error code otherwise.
+ */
+static int xilinx_ai_engine_debugfs_init(struct platform_device *pdev,
+					 struct irq_sim *irq_sim)
+{
+	int ret;
+	struct dentry *debugfs_dir, *debugfs_file;
+
+	debugfs_dir = debugfs_create_dir("xilinx-ai-engine", NULL);
+	if (!debugfs_dir)
+		return -ENODEV;
+
+	debugfs_file = debugfs_create_file(dev_name(&pdev->dev), 0644,
+					   debugfs_dir, irq_sim, &debugfs_ops);
+	if (!debugfs_file) {
+		ret = -ENODEV;
+		goto err_out;
+	}
+
+	return 0;
+
+err_out:
+	debugfs_remove_recursive(debugfs_dir);
+	return ret;
+}
+
+/**
+ * xilinx_ai_engine_simulate_irq - Simulate the irq
+ * @pdev: platform device to simulate irq for
+ *
+ * Simulate the irq so the irq can be generated from user. This is only for
+ * debugging purpose.
+ *
+ * Return: 0 for success, error code otherwise.
+ */
+static int xilinx_ai_engine_simulate_irq(struct platform_device *pdev)
+{
+	struct irq_sim *irq_sim;
+	int irq, ret;
+
+	irq_sim = devm_kzalloc(&pdev->dev, sizeof(*irq_sim), GFP_KERNEL);
+	if (!irq_sim)
+		return -ENOMEM;
+
+	/*
+	 * Sometimes, the returned base value is 0, so allocate 2 irqs, and
+	 * always use the 2nd one.
+	 */
+	irq = devm_irq_sim_init(&pdev->dev, irq_sim, 2);
+	if (irq < 0)
+		return irq;
+
+	ret = xilinx_ai_engine_debugfs_init(pdev, irq_sim);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed create debugfs for sim irq");
+		return ret;
+	}
+
+	return irq_sim_irqnum(irq_sim, 1);
+}
+
+#else
+
+static int xilinx_ai_engine_simulate_irq(struct platform_device *pdev)
+{
+	return -ENODEV;
+}
+
+#endif
+
 static int xilinx_ai_engine_mem_index(struct uio_info *info,
 				      struct vm_area_struct *vma)
 {
@@ -127,8 +225,11 @@ static int xilinx_ai_engine_probe(struct platform_device *pdev)
 	}
 
 	/* Interrupt is optional */
-	if (ret < 0)
-		ret = UIO_IRQ_CUSTOM;
+	if (ret < 0) {
+		ret = xilinx_ai_engine_simulate_irq(pdev);
+		if (ret < 0)
+			ret = UIO_IRQ_CUSTOM;
+	}
 	pdata->uioinfo.irq = ret;
 
 	ret = platform_device_add_data(uio, pdata, sizeof(*pdata));