pc_serial: convert irq handler to use DPC

Let's hope we won't loose data because it.

We have to cache the value of IIR read from IsInterruptPending(),
because some conditions are acknowledged only by reading it...

src/add-ons/kernel/drivers/ports/pc_serial/Driver.cpp

@@ -10,6 +10,7 @@
  * Distributed under the terms of the MIT License.
  */
 #include <KernelExport.h>
+#include <dpc.h>
 #include <Drivers.h>
 #include <image.h>
 #include <malloc.h>
@@ -27,6 +28,8 @@ config_manager_for_driver_module_info *gConfigManagerModule = NULL;
 isa_module_info *gISAModule = NULL;
 pci_module_info *gPCIModule = NULL;
 tty_module_info *gTTYModule = NULL;
+dpc_module_info *gDPCModule = NULL;
+void* gDPCHandle = NULL;
 sem_id gDriverLock = -1;
 bool gHandleISA = false;
 
@@ -653,6 +656,10 @@ init_driver()
 
 	TRACE_FUNCALLS("> init_driver()\n");
 
+	status = get_module(B_DPC_MODULE_NAME, (module_info **)&gDPCModule);
+	if (status < B_OK)
+		goto err_dpc;
+
 	status = get_module(B_TTY_MODULE_NAME, (module_info **)&gTTYModule);
 	if (status < B_OK)
 		goto err_tty;
@@ -670,6 +677,11 @@ init_driver()
 	if (status < B_OK)
 		goto err_cm;
 
+	status = gDPCModule->new_dpc_queue(&gDPCHandle, "pc_serial irq",
+		B_REAL_TIME_PRIORITY);
+	if (status != B_OK)
+		goto err_dpcq;
+
 	for (int32 i = 0; i < DEVICES_COUNT; i++)
 		gSerialDevices[i] = NULL;
 
@@ -697,6 +709,9 @@ init_driver()
 //err_none:
 	delete_sem(gDriverLock);
 err_sem:
+	gDPCModule->delete_dpc_queue(gDPCHandle);
+	gDPCHandle = NULL;
+err_dpcq:
 	put_module(B_CONFIG_MANAGER_FOR_DRIVER_MODULE_NAME);
 err_cm:
 	put_module(B_ISA_MODULE_NAME);
@@ -705,6 +720,8 @@ err_isa:
 err_pci:
 	put_module(B_TTY_MODULE_NAME);
 err_tty:
+	put_module(B_DPC_MODULE_NAME);
+err_dpc:
 	TRACE_FUNCRET("< init_driver() returns %s\n", strerror(status));
 	return status;
 }
@@ -735,10 +752,13 @@ uninit_driver()
 		free(gDeviceNames[i]);
 
 	delete_sem(gDriverLock);
+	gDPCModule->delete_dpc_queue(gDPCHandle);
+	gDPCHandle = NULL;
 	put_module(B_CONFIG_MANAGER_FOR_DRIVER_MODULE_NAME);
 	put_module(B_ISA_MODULE_NAME);
 	put_module(B_PCI_MODULE_NAME);
 	put_module(B_TTY_MODULE_NAME);
+	put_module(B_DPC_MODULE_NAME);
 
 	TRACE_FUNCRET("< uninit_driver() returns\n");
 }
@@ -764,28 +784,32 @@ pc_serial_service(struct tty *tty, uint32 op, void *buffer, size_t length)
 }
 
 
+static void
+pc_serial_dpc(void *arg)
+{
+	SerialDevice *master = (SerialDevice *)arg;
+	TRACE_FUNCALLS("> pc_serial_dpc(%p)\n", arg);
+	master->InterruptHandler();
+}
+
+
 int32
 pc_serial_interrupt(void *arg)
 {
-	int32 ret;
-	SerialDevice *master = (SerialDevice *)arg;
+	SerialDevice *device = (SerialDevice *)arg;
 	TRACE_FUNCALLS("> pc_serial_interrupt(%p)\n", arg);
 
-	if (!master)
+	if (!device)
 		return B_UNHANDLED_INTERRUPT;
 
-	ret = master->InterruptHandler();
-	return ret;
-
-
-	for (int32 i = 0; i < DEVICES_COUNT; i++) {
-		if (gSerialDevices[i] && gSerialDevices[i]->Master() == master) {
-			ret = gSerialDevices[i]->InterruptHandler();
-			// XXX: handle more than 1 ?
-			if (ret != B_UNHANDLED_INTERRUPT) {
-				TRACE_FUNCRET("< pc_serial_interrupt() returns: true\n");
-				return ret;
-			}
+	if (device->IsInterruptPending()) {
+		status_t err;
+		err = gDPCModule->queue_dpc(gDPCHandle, pc_serial_dpc, device);
+		if (err != B_OK)
+			dprintf(DRIVER_NAME ": error queing irq: %s\n", strerror(err));
+		else {
+			TRACE_FUNCRET("< pc_serial_interrupt() returns: handled\n");
+			return B_HANDLED_INTERRUPT;
 		}
 	}
 

src/add-ons/kernel/drivers/ports/pc_serial/SerialDevice.cpp

@@ -29,6 +29,7 @@ SerialDevice::SerialDevice(const struct serial_support_descriptor *device,
 		fIOBase(ioBase),
 		fIRQ(irq),
 		fMaster(master),
+		fCachedIIR(0x1),
 		fReadBufferAvail(0),
 		fReadBufferIn(0),
 		fReadBufferOut(0),
@@ -320,6 +321,19 @@ SerialDevice::Service(struct tty *tty, uint32 op, void *buffer, size_t length)
 }
 
 
+bool
+SerialDevice::IsInterruptPending()
+{
+	TRACE(("IsInterruptPending()\n"));
+
+	// because reading the IIR acknowledges some IRQ conditions,
+	// the next time we'll read we'll miss the IRQ condition
+	// so we just cache the value for the real handler
+	fCachedIIR = ReadReg8(IIR);
+	return ((fCachedIIR & IIR_PENDING) == 0); // 0 means yes
+}
+
+
 int32
 SerialDevice::InterruptHandler()
 {
@@ -329,7 +343,9 @@ SerialDevice::InterruptHandler()
 	uint8 iir, lsr, msr;
 	TRACE(("InterruptHandler()\n"));
 
-	while (((iir = ReadReg8(IIR)) & IIR_PENDING) == 0) { // 0 means yes
+	// start with the first (cached) irq condition
+	iir = fCachedIIR;
+	while ((iir & IIR_PENDING) == 0) { // 0 means yes
 		int fifoavail = 1;
 		int avail;
 		int i;
@@ -399,6 +415,9 @@ SerialDevice::InterruptHandler()
 		}
 		ret = B_HANDLED_INTERRUPT;
 		TRACE(("IRQ:h\n"));
+
+		// check the next IRQ condition
+		iir = ReadReg8(IIR);
 	}
 
 	TRACE_FUNCRET("< IRQ:%d\n", ret);

src/add-ons/kernel/drivers/ports/pc_serial/SerialDevice.h

@@ -46,6 +46,7 @@ static	SerialDevice *			MakeDevice(struct serial_config_descriptor
 		bool					Service(struct tty *tty, uint32 op,
 									void *buffer, size_t length);
 
+		bool					IsInterruptPending();
 		int32					InterruptHandler();
 
 		status_t				Open(uint32 flags);
@@ -112,6 +113,9 @@ static	void					InterruptCallbackFunction(void *cookie,
 		/* line coding */
 		//usb_serial_line_coding	fLineCoding;
 
+		/* deferred interrupt */
+		uint8					fCachedIIR;	// cached IRQ condition
+
 		/* data buffers */
 		char					fReadBuffer[DEF_BUFFER_SIZE];
 		int32					fReadBufferAvail;