[PATCH] libata drain fifo on stuck DRQ HSM violation

From: Mark Lord
Date: Thu Sep 27 2007 - 23:56:49 EST

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@xxxxxxxxx>

--- old/drivers/ata/libata-sff.c 2007-04-26 12:02:46.000000000 -0400
+++ linux/drivers/ata/libata-sff.c 2007-04-29 08:29:27.000000000 -0400
@@ -413,6 +413,24 @@

+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.
+ */
+ if ((stat & ATA_DRQ) && (!qc || qc->dma_dir != DMA_TO_DEVICE)) {
+ unsigned int i, limit = 512;
+ printk("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("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
@@ -469,7 +487,7 @@

- ata_chk_status(ap);
+ ata_drain_fifo(ap, qc);

spin_unlock_irqrestore(ap->lock, flags);
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