[PATCH] IDE dma reset for sl82c105

[Todd Inglett]

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I have found that the IDE controller on a w83c553f (a sl82c105 function) 
can get into a hung state if the interrupt line is wired to INTC and a 
timeout occurs.  The following patch implements a hard reset for the 
controller as documented in a Windbond engineering notice.

This patch needs some testing and there appears to be no maintainer for 
the sl83c105 IDE driver :(.  The conditions to repeat the problem are 
that the controller must be wired for PCI INTC, DMA must be in use, and 
a timeout error must occur (try mounting a music CD).  My fix checks for 
INTC configuration so hopefully this patch will only affect systems that 
exhibit the hang.  I have tested it on an IBM pSeries model 610 which 
has the hardware operating in this mode.

The patch should apply to 2.5.13 - 2.5.16 (at least).

-todd

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--- drivers/ide/sl82c105.c	16 Aug 2001 13:50:23 -0000	1.3
+++ drivers/ide/sl82c105.c	17 Dec 2001 19:14:28 -0000
@@ -156,6 +156,29 @@
 }
 
 /*
+ * Reset the controller.
+ * If we are using INTC under a w83c553 we need to use a magic test
+ * bit to do this.  Return zero if successful (or applicable).
+ * 
+ */
+static int sl82c105_hard_reset(ide_drive_t *drive)
+{
+	ide_hwif_t *hwif = HWIF(drive);
+	struct pci_dev *dev = hwif->pci_dev;
+	unsigned int reg;
+
+	pci_read_config_dword(dev, 0x40, &reg);	/* LEGIRQ register */
+	if (reg & (1<<11)) {	/* Using INTC? */
+		printk("sl82c105: resetting device\n");
+		pci_read_config_dword(dev, 0x7e, &reg);
+		pci_write_config_word(dev, 0x7e, reg | (1<<2));
+		pci_write_config_word(dev, 0x7e, reg & (~(1<<2)));
+		return 0;
+	}
+	return 1;
+}
+
+/*
  * Our own dmaproc, only to intercept ide_dma_check
  */
 static int sl82c105_dmaproc(ide_dma_action_t func, ide_drive_t *drive)
@@ -171,6 +194,11 @@
 	case ide_dma_off:
 		config_for_pio(drive, 4, 0);
 		break;
+	case ide_dma_lostirq:
+	case ide_dma_timeout:
+	        if (sl82c105_hard_reset(drive) == 0)
+			return 0;
+	        break;
 	default:
 		break;
 	}

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