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SubjectRe: SCSI or libata problem with an RDX removable disk
Alan Cox wrote:
>> Sep 4 08:03:08 devsni1 kernel: ata4: port is slow to respond, please be patient (Status 0xd0)
>> Sep 4 08:03:31 devsni1 kernel: ata4: port failed to respond (30 secs, Status 0xd0)
>> Sep 4 08:03:31 devsni1 kernel: ata4: soft resetting port
>> Sep 4 08:03:32 devsni1 kernel: ATA: abnormal status 0xD0 on port 0x0001d807
>> Sep 4 08:03:32 devsni1 last message repeated 4 times
>
> Your disk went offline and then refused to come back when the link was
> reset. The initial trigger appears to have been the drive, the fact it
> didn't come back could either be the drive or a controller problem. We've
> seen a few cases where devices or controllers fail to recover from one
> end being stuck expecting data.
>
> Mark Lord did some patches to try and drain data in this case but I don't
> remember if they were merged yet.
..

That would be this patch, currently not merged, not maintained,
and probably needs rework for some chipsets. But for the record:


Tejun Heo wrote:
> Jeff Garzik wrote:
>> Tejun Heo wrote:
>>> Alan Cox wrote:
>>>>> I think there have been enough cases where this draining was necessary.
>>>>> IIRC, ata_piix was involved in those cases, right? If so, can you
>>>>> please submit a patch which applies this only to affected controllers?
>>>>> I don't feel too confident about applying this to all SFF controllers.
>>>> Old IDE does it on all controllers bar a couple. So we have a very good
>>>> knowledge of what does/doesn't work. The one that needs care in old ide
>>>> is an ordering issue where a state machine reset done first causes the
>>>> drain of the I/O to hang.
>>> Hmmm... So, do we apply draining to all PATA? Or is ata_piix SATA
>>> affected too?
>> I would think all SFF controllers, since a lot of first gen SATA are
>> really bridged solutions. If they are flagging DRQ, I say oblige them :)
>
> Alright, then the posted patch should be good enough. Mark, can you be
> bothered to regenerate the patch and post it one more time (again)? It
> seems we all agree the update is needed.

I think this original patch still applies cleanly on at least 2.6.23-rc7.

Drain up to 512 words from host/bridge FIFO on stuck DRQ HSM violation,
rather than just getting stuck there forever.

Signed-off-by: Mark Lord <mlord@pobox.com>
---

--- old/drivers/ata/libata-sff.c 2007-09-28 09:29:22.000000000 -0400
+++ linux/drivers/ata/libata-sff.c 2007-09-28 09:39:44.000000000 -0400
@@ -420,6 +420,28 @@
ap->ops->irq_on(ap);
}

+static void ata_drain_fifo(struct ata_port *ap, struct ata_queued_cmd *qc)
+{
+ u8 stat = ata_chk_status(ap);
+ /*
+ * Try to clear stuck DRQ if necessary,
+ * by reading/discarding up to two sectors worth of data.
+ */
+ if ((stat & ATA_DRQ) && (!qc || qc->dma_dir != DMA_TO_DEVICE)) {
+ unsigned int i;
+ unsigned int limit = qc ? qc->sect_size : ATA_SECT_SIZE;
+
+ printk(KERN_WARNING "Draining up to %u words from data FIFO.\n",
+ limit);
+ for (i = 0; i < limit ; ++i) {
+ ioread16(ap->ioaddr.data_addr);
+ if (!(ata_chk_status(ap) & ATA_DRQ))
+ break;
+ }
+ printk(KERN_WARNING "Drained %u/%u words.\n", i, limit);
+ }
+}
+
/**
* ata_bmdma_drive_eh - Perform EH with given methods for BMDMA controller
* @ap: port to handle error for
@@ -476,7 +498,7 @@
}

ata_altstatus(ap);
- ata_chk_status(ap);
+ ata_drain_fifo(ap, qc);
ap->ops->irq_clear(ap);

spin_unlock_irqrestore(ap->lock, flags);

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