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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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