[SCSI] mac_esp: fix for quadras with two esp chips

On the Quadra 900 and 950 there are two ESP chips sharing one IRQ. Because
the shared IRQ is edge-triggered, we must make sure that an IRQ transition
from one chip doesn't go unnoticed when the shared IRQ is already active
due to the other. This patch prevents interrupts getting lost so that both
SCSI busses may be used simultaneously.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

drivers/scsi/mac_esp.c

@@ -53,7 +53,8 @@ struct mac_esp_priv {
 	void __iomem *pdma_io;
 	int error;
 };
-static struct platform_device *internal_esp, *external_esp;
+static struct platform_device *internal_pdev, *external_pdev;
+static struct esp *esp_chips[2];
 
 #define MAC_ESP_GET_PRIV(esp) ((struct mac_esp_priv *) \
 			       platform_get_drvdata((struct platform_device *) \
@@ -443,6 +444,32 @@ static u32 mac_esp_dma_length_limit(struct esp *esp, u32 dma_addr, u32 dma_len)
 	return dma_len > 0xFFFF ? 0xFFFF : dma_len;
 }
 
+static irqreturn_t mac_scsi_esp_intr(int irq, void *dev_id)
+{
+	int got_intr;
+
+	/*
+	 * This is an edge triggered IRQ, so we have to be careful to
+	 * avoid missing a transition when it is shared by two ESP devices.
+	 */
+
+	do {
+		got_intr = 0;
+		if (esp_chips[0] &&
+		    (mac_esp_read8(esp_chips[0], ESP_STATUS) & ESP_STAT_INTR)) {
+			(void)scsi_esp_intr(irq, esp_chips[0]);
+			got_intr = 1;
+		}
+		if (esp_chips[1] &&
+		    (mac_esp_read8(esp_chips[1], ESP_STATUS) & ESP_STAT_INTR)) {
+			(void)scsi_esp_intr(irq, esp_chips[1]);
+			got_intr = 1;
+		}
+	} while (got_intr);
+
+	return IRQ_HANDLED;
+}
+
 static struct esp_driver_ops mac_esp_ops = {
 	.esp_write8       = mac_esp_write8,
 	.esp_read8        = mac_esp_read8,
@@ -557,10 +584,16 @@ static int __devinit esp_mac_probe(struct platform_device *dev)
 	}
 
 	host->irq = IRQ_MAC_SCSI;
-	err = request_irq(host->irq, scsi_esp_intr, IRQF_SHARED, "Mac ESP",
-			  esp);
-	if (err < 0)
-		goto fail_free_priv;
+	esp_chips[dev->id] = esp;
+	mb();
+	if (esp_chips[!dev->id] == NULL) {
+		err = request_irq(host->irq, mac_scsi_esp_intr, 0,
+		                  "Mac ESP", NULL);
+		if (err < 0) {
+			esp_chips[dev->id] = NULL;
+			goto fail_free_priv;
+		}
+	}
 
 	err = scsi_esp_register(esp, &dev->dev);
 	if (err)
@@ -569,7 +602,8 @@ static int __devinit esp_mac_probe(struct platform_device *dev)
 	return 0;
 
 fail_free_irq:
-	free_irq(host->irq, esp);
+	if (esp_chips[!dev->id] == NULL)
+		free_irq(host->irq, esp);
 fail_free_priv:
 	kfree(mep);
 fail_free_command_block:
@@ -588,7 +622,9 @@ static int __devexit esp_mac_remove(struct platform_device *dev)
 
 	scsi_esp_unregister(esp);
 
-	free_irq(irq, esp);
+	esp_chips[dev->id] = NULL;
+	if (!(esp_chips[0] || esp_chips[1]))
+		free_irq(irq, NULL);
 
 	kfree(mep);
 
@@ -615,19 +651,18 @@ static int __init mac_esp_init(void)
 	if (err)
 		return err;
 
-	internal_esp = platform_device_alloc(DRV_MODULE_NAME, 0);
-	if (internal_esp && platform_device_add(internal_esp)) {
-		platform_device_put(internal_esp);
-		internal_esp = NULL;
+	internal_pdev = platform_device_alloc(DRV_MODULE_NAME, 0);
+	if (internal_pdev && platform_device_add(internal_pdev)) {
+		platform_device_put(internal_pdev);
+		internal_pdev = NULL;
 	}
-
-	external_esp = platform_device_alloc(DRV_MODULE_NAME, 1);
-	if (external_esp && platform_device_add(external_esp)) {
-		platform_device_put(external_esp);
-		external_esp = NULL;
+	external_pdev = platform_device_alloc(DRV_MODULE_NAME, 1);
+	if (external_pdev && platform_device_add(external_pdev)) {
+		platform_device_put(external_pdev);
+		external_pdev = NULL;
 	}
 
-	if (internal_esp || external_esp) {
+	if (internal_pdev || external_pdev) {
 		return 0;
 	} else {
 		platform_driver_unregister(&esp_mac_driver);
@@ -639,13 +674,13 @@ static void __exit mac_esp_exit(void)
 {
 	platform_driver_unregister(&esp_mac_driver);
 
-	if (internal_esp) {
-		platform_device_unregister(internal_esp);
-		internal_esp = NULL;
+	if (internal_pdev) {
+		platform_device_unregister(internal_pdev);
+		internal_pdev = NULL;
 	}
-	if (external_esp) {
-		platform_device_unregister(external_esp);
-		external_esp = NULL;
+	if (external_pdev) {
+		platform_device_unregister(external_pdev);
+		external_pdev = NULL;
 	}
 }