[PATCH 2.6.13] libata: use common pci remove in ahci

[PATCH 2.6.13] libata: use common pci remove in ahci

[Brett Russ]

Jeff,

This looked prime to cut since ahci_remove_one() was a functionally
identical to ata_pci_remove_one() except for the interrupt disable
(have_msi) bits, which fit nicely into ahci_host_stop().  However,

1) Will it work?

2) Isn't it wrong for the IRQ disable at the chip to occur *after*
free_irq() is called to disconnect the handler (independent of
question 1...since this is the case currently)?  Granted, all of the
ports have gone through scsi_remove_host() but theoretically there
still is a possibility the chip could interrupt.

If I'm wrong on both counts I'll blame it on need for sleep... :-)
BR

This patch depends on the PCI INTx patch (but will probably work w/o):
http://lkml.org/lkml/2005/8/15/165


Signed-off-by: Brett Russ <russb@emc.com>


Index: linux-2.6.13/drivers/scsi/ahci.c
===================================================================
--- linux-2.6.13.orig/drivers/scsi/ahci.c
+++ linux-2.6.13/drivers/scsi/ahci.c
@@ -187,7 +187,6 @@ static void ahci_qc_prep(struct ata_queu
 static u8 ahci_check_status(struct ata_port *ap);
 static u8 ahci_check_err(struct ata_port *ap);
 static inline int ahci_host_intr(struct ata_port *ap, struct ata_queued_cmd *qc);
-static void ahci_remove_one (struct pci_dev *pdev);
 
 static Scsi_Host_Template ahci_sht = {
 	.module			= THIS_MODULE,
@@ -277,7 +276,7 @@ static struct pci_driver ahci_pci_driver
 	.name			= DRV_NAME,
 	.id_table		= ahci_pci_tbl,
 	.probe			= ahci_init_one,
-	.remove			= ahci_remove_one,
+	.remove			= ata_pci_remove_one,
 };
 
 
@@ -294,6 +293,13 @@ static inline void *ahci_port_base (void
 static void ahci_host_stop(struct ata_host_set *host_set)
 {
 	struct ahci_host_priv *hpriv = host_set->private_data;
+	struct pci_dev *pdev = to_pci_dev(host_set->dev);
+
+	if (hpriv->flags & AHCI_FLAG_MSI)
+		pci_disable_msi(pdev);
+	else
+		pci_intx(pdev, 0);
+
 	kfree(hpriv);
 
 	ata_host_stop(host_set);
@@ -1036,43 +1042,6 @@ err_out:
 	return rc;
 }
 
-static void ahci_remove_one (struct pci_dev *pdev)
-{
-	struct device *dev = pci_dev_to_dev(pdev);
-	struct ata_host_set *host_set = dev_get_drvdata(dev);
-	struct ahci_host_priv *hpriv = host_set->private_data;
-	struct ata_port *ap;
-	unsigned int i;
-	int have_msi;
-
-	for (i = 0; i < host_set->n_ports; i++) {
-		ap = host_set->ports[i];
-
-		scsi_remove_host(ap->host);
-	}
-
-	have_msi = hpriv->flags & AHCI_FLAG_MSI;
-	free_irq(host_set->irq, host_set);
-
-	for (i = 0; i < host_set->n_ports; i++) {
-		ap = host_set->ports[i];
-
-		ata_scsi_release(ap->host);
-		scsi_host_put(ap->host);
-	}
-
-	host_set->ops->host_stop(host_set);
-	kfree(host_set);
-
-	if (have_msi)
-		pci_disable_msi(pdev);
-	else
-		pci_intx(pdev, 0);
-	pci_release_regions(pdev);
-	pci_disable_device(pdev);
-	dev_set_drvdata(dev, NULL);
-}
-
 static int __init ahci_init(void)
 {
 	return pci_module_init(&ahci_pci_driver);

Re: [PATCH 2.6.13] libata: use common pci remove in ahci

[Jeff Garzik]

Brett Russ wrote:
> Jeff,
> 
> This looked prime to cut since ahci_remove_one() was a functionally
> identical to ata_pci_remove_one() except for the interrupt disable
> (have_msi) bits, which fit nicely into ahci_host_stop().  However,
> 
> 1) Will it work?
> 
> 2) Isn't it wrong for the IRQ disable at the chip to occur *after*
> free_irq() is called to disconnect the handler (independent of
> question 1...since this is the case currently)?  Granted, all of the
> ports have gone through scsi_remove_host() but theoretically there
> still is a possibility the chip could interrupt.
> 
> If I'm wrong on both counts I'll blame it on need for sleep... :-)


Moving AHCI away from ata_pci_remove_one() was actually intentional. 
This gives the driver a bit more freedom:  legacy region handling and 
->host_stop() became unnecessary.  Also, I was concerned that 
ata_pci_remove_one() might grow into a one-size-fits-all unmaintainable 
behemoth.

Short term, if one were being obsessive, a potential cleanup could be to 
make common the two loops in ahci_remove_one()/ata_pci_remove_one().

Long term, libata driver API should become more like the 
register_foo()/unregister_foo() interfaces you see elsewhere in the 
kernel.  That direction has the potential to shake up the current code 
path through ata_pci_remove_one().

So... your patch, while technically correct, is going in the opposite 
direction to where I want to go :)

	Jeff

Re: [PATCH 2.6.13] libata: use common pci remove in ahci

[Brett Russ]

Jeff Garzik wrote:
> Brett Russ wrote:
>> 2) Isn't it wrong for the IRQ disable at the chip to occur *after*
>> free_irq() is called to disconnect the handler (independent of
>> question 1...since this is the case currently)?  Granted, all of the
>> ports have gone through scsi_remove_host() but theoretically there
>> still is a possibility the chip could interrupt.
>>
>> If I'm wrong on both counts I'll blame it on need for sleep... :-)
> 
> 
> 
> Moving AHCI away from ata_pci_remove_one() was actually intentional. 
> This gives the driver a bit more freedom:  legacy region handling and 
> ->host_stop() became unnecessary.  Also, I was concerned that 
> ata_pci_remove_one() might grow into a one-size-fits-all unmaintainable 
> behemoth.
> 
> Short term, if one were being obsessive, a potential cleanup could be to 
> make common the two loops in ahci_remove_one()/ata_pci_remove_one().
> 
> Long term, libata driver API should become more like the 
> register_foo()/unregister_foo() interfaces you see elsewhere in the 
> kernel.  That direction has the potential to shake up the current code 
> path through ata_pci_remove_one().
> 
> So... your patch, while technically correct, is going in the opposite 
> direction to where I want to go :)


Good to know, thanks for explaining the goals.  How about question #2 above?

Thanks,
BR

Re: [PATCH 2.6.13] libata: use common pci remove in ahci

[Jeff Garzik]

Brett Russ wrote:
> Jeff Garzik wrote:
>> Brett Russ wrote:
>>> 2) Isn't it wrong for the IRQ disable at the chip to occur *after*
>>> free_irq() is called to disconnect the handler (independent of
>>> question 1...since this is the case currently)?  Granted, all of the
>>> ports have gone through scsi_remove_host() but theoretically there
>>> still is a possibility the chip could interrupt.

Answer:  depends on hardware.

For all hardware, the conditions that generate interrupts should be shut 
down, and then free_irq() is called after that.

Some hardware only needs per-port disable, or nothing besides clearing 
any commands, to ensure that interrupts from that hardware are disabled 
(this excludes shared interrupts, of course).

This logic is another reason why a driver author may choose to implement 
their own PCI ->remove() hook, rather than using the generic 
ata_pci_remove_one().  Eliminates the need for a ->host_stop() hook 
implementation, and allows one to perform tasks before calling 
free_irq(), as well as tasks after the call (normal ->host_stop stuff).

	Jeff