libata: Keep shadow last_ctl up to date during resets

libata keeps a shadow copy of the ATA CTL register (which is write only), and only writes to the hardware when the required value doesn't match the shadow. However this copy wasn't being maintained when performing reset functions. This could cause problems for the first operation after a reset when the correct value might not be written to the CTL register.

This problem was observed when hotplugging a drive: the identify command was being issued with interrupts enabled, when they should have been disabled.

Signed-off-by Stuart Menefy <[email protected]>

Hello,

Quoted 10 lines · Stuart MENEFY

libata keeps a shadow copy of the ATA CTL register (which is write only), and only writes to the hardware when the required value doesn't match the shadow. However this copy wasn't being maintained when performing reset functions. This could cause problems for the first operation after a reset when the correct value might not be written to the CTL register.

This problem was observed when hotplugging a drive: the identify command was being issued with interrupts enabled, when they should have been disabled.

Quoted 1 line

Signed-off-by Stuart Menefy <[email protected]>

Nice catch. Maybe a nice addition would be a ata_sff_write_to_ctl() or something which always does the right thing.

Acked-by Tejun Heo <[email protected]>

Quoted 16 lines · Tejun Heo

Hello,

Quoted 12 lines · Stuart MENEFY

libata keeps a shadow copy of the ATA CTL register (which is write only),
and only writes to the hardware when the required value doesn't match the shadow. However this copy wasn't being maintained when performing reset functions. This could cause problems for the first operation after a reset when the correct value might not be written to the CTL register.

This problem was observed when hotplugging a drive: the identify command was being issued with interrupts enabled, when they should have been disabled.

Signed-off-by Stuart Menefy <[email protected]>

Quoted 4 lines

Nice catch. Maybe a nice addition would be a ata_sff_write_to_ctl() or something which always does the right thing.

Acked-by Tejun Heo <[email protected]>

..

Mmm.. I wonder if this is severe enough to warrant backporting to -stable for the past couple of releases?

libata keeps a shadow copy of the ATA CTL register (which is write only), and only writes to the hardware when the required value doesn't match the shadow. However this copy wasn't being maintained when performing reset functions. This could cause problems for the first operation after a reset when the correct value might not be written to the CTL register.

This problem was observed when hotplugging a drive: the identify command was being issued with interrupts enabled, when they should have been disabled.

Signed-off-by Stuart Menefy <[email protected]>

---
 linux-2.6/drivers/ata/libata-sff.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Index: linux-2.6/drivers/ide/ide-dma-sff.c
===================================================================

drivers/ata/libata-sff.c +4 -1

@@ -2066,6 +2066,7 @@ static int ata_bus_softreset(struct ata_
 	iowrite8(ap->ctl | ATA_SRST, ioaddr->ctl_addr);
 	udelay(20);	/* FIXME: flush */
 	iowrite8(ap->ctl, ioaddr->ctl_addr);
+	ap->last_ctl = ap->ctl;
 
 	/* wait the port to become ready */
 	return ata_sff_wait_after_reset(&ap->link, devmask, deadline);

@@ -2190,8 +2191,10 @@ void ata_sff_postreset(struct ata_link *
 	}
 
 	/* set up device control */
-	if (ap->ioaddr.ctl_addr)
+	if (ap->ioaddr.ctl_addr) {
 		iowrite8(ap->ctl, ap->ioaddr.ctl_addr);
+		ap->last_ctl = ap->ctl;
+	}
 }
 EXPORT_SYMBOL_GPL(ata_sff_postreset);