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SubjectRe: [PATCH v2 4/4] ata: add ata port runtime PM callbacks
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On Mon, 2011-11-14 at 23:31 +0800, Alan Stern wrote:
> On Mon, 14 Nov 2011, Lin Ming wrote:
>
> > Current patches has a bug that system suspend fails if ata port was
> > runtime suspended.
> >
> > disk suspend issues sync cache and stop device commands that obviously
> > need ata port to be active. So we need to runtime resume ata port first.
>
> This is wrong. If the port is already suspended then so are all the
> drives below the port. Hence there is no need to sync the cache or
> stop the device.

Ah, got it now!

>
> > Alan, Tejun
> >
> > How about below fix?
> >
> > diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> > index fa3a591..ebb87fbf 100644
> > --- a/drivers/scsi/sd.c
> > +++ b/drivers/scsi/sd.c
> > @@ -50,6 +50,7 @@
> > #include <linux/string_helpers.h>
> > #include <linux/async.h>
> > #include <linux/slab.h>
> > +#include <linux/pm_runtime.h>
> > #include <asm/uaccess.h>
> > #include <asm/unaligned.h>
> >
> > @@ -2762,6 +2763,14 @@ static int sd_suspend(struct device *dev, pm_message_t mesg)
> > if (!sdkp)
> > return 0; /* this can happen */
> >
> > + /*
> > + * Resume parent device to handle sync cache and
> > + * stop device commands
> > + */
> > + ret = pm_runtime_get_sync(dev->parent);
> > + if (ret)
> > + goto exit;
> > +
> > if (sdkp->WCE) {
> > sd_printk(KERN_NOTICE, sdkp, "Synchronizing SCSI cache\n");
> > ret = sd_sync_cache(sdkp);
>
> This is not the right approach. You should look instead at
> scsi_dev_type_suspend() in scsi_pm.c. If the device is already runtime
> suspended then the routine should return immediately.

How about below?

diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c
index d329f8b..94b60bd 100644
--- a/drivers/scsi/scsi_pm.c
+++ b/drivers/scsi/scsi_pm.c
@@ -20,6 +20,9 @@ static int scsi_dev_type_suspend(struct device *dev, pm_message_t msg)
struct device_driver *drv;
int err;

+ if (pm_runtime_suspended(dev))
+ return 0;
+
err = scsi_device_quiesce(to_scsi_device(dev));
if (err == 0) {
drv = dev->driver;

>
> Alan Stern
>




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