[PATCH] ide-cd: Handle strange interrupt on the Intel ESB2

The ESB2 appears to emit spurious DMA interrupts when configured for native
mode and handling ATAPI devices.  Stratus were able to pin this bug down and
produce a patch.  This is a rework which applies the fixup only to the ESB2
(for now).  We can apply it to other chips later if the same problem is found.

This code has been tested and confirmed to fix the problem on the tested
systems.

Signed-off-by: Alan Cox <alan@redhat.com>
(Most of the hard work done by Stratus however)
Cc: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 12 insertions, 0 deletions

diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c
index 88214943d00a..5969cec58dc1 100644
--- a/drivers/ide/ide-cd.c
+++ b/drivers/ide/ide-cd.c
@@ -687,8 +687,15 @@ static void ide_dump_status_no_sense(ide_drive_t *drive, const char *msg, u8 sta
 static int cdrom_decode_status(ide_drive_t *drive, int good_stat, int *stat_ret)
 {
         struct request *rq = HWGROUP(drive)->rq;
+        ide_hwif_t *hwif = HWIF(drive);
         int stat, err, sense_key;
         
+        /* We may have bogus DMA interrupts in PIO state here */
+        if (HWIF(drive)->dma_status && hwif->atapi_irq_bogon) {
+                stat = hwif->INB(hwif->dma_status);
+                /* Should we force the bit as well ? */
+                hwif->OUTB(stat, hwif->dma_status);
+        }
         /* Check for errors. */
         stat = HWIF(drive)->INB(IDE_STATUS_REG);
         if (stat_ret)
diff --git a/drivers/ide/pci/piix.c b/drivers/ide/pci/piix.c
index cdc3aab9ebcb..b1e9a8eba6b6 100644
--- a/drivers/ide/pci/piix.c
+++ b/drivers/ide/pci/piix.c
@@ -505,6 +505,10 @@ static void __devinit init_hwif_piix(ide_hwif_t *hwif)
                 /* This is a painful system best to let it self tune for now */
                 return;
         }
+        /* ESB2 appears to generate spurious DMA interrupts in PIO mode
+           when in native mode */
+        if (hwif->pci_dev->device == PCI_DEVICE_ID_INTEL_ESB2_18)
+                hwif->atapi_irq_bogon = 1;
 
         hwif->autodma = 0;
         hwif->tuneproc = &piix_tune_drive;
diff --git a/include/linux/ide.h b/include/linux/ide.h
index 9c2050293f17..64e070f62a87 100644
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -796,6 +796,7 @@ typedef struct hwif_s {
         unsigned        sg_mapped  : 1; /* sg_table and sg_nents are ready */
         unsigned        no_io_32bit : 1; /* 1 = can not do 32-bit IO ops */
         unsigned        err_stops_fifo : 1; /* 1=data FIFO is cleared by an error */
+        unsigned        atapi_irq_bogon : 1; /* Generates spurious DMA interrupts in PIO mode */
 
         struct device   gendev;
         struct completion gendev_rel_comp; /* To deal with device release() */