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    SubjectRe: [RFC PATCH 01/14] coresight: etm4x: Skip save/restore before device registration
    Hi Suzuki,

    I have starte to review this - comments will be scattered over a few days.

    On Wed, Jul 22, 2020 at 06:20:27PM +0100, Suzuki K Poulose wrote:
    > Skip cpu save/restore before the coresight device is registered.
    >
    > Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
    > Cc: Mike Leach <mike.leach@linaro.org>
    > Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
    > ---
    > drivers/hwtracing/coresight/coresight-etm4x.c | 16 +++++++++++++++-
    > 1 file changed, 15 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
    > index 6d7d2169bfb2..cb83fb77ded6 100644
    > --- a/drivers/hwtracing/coresight/coresight-etm4x.c
    > +++ b/drivers/hwtracing/coresight/coresight-etm4x.c
    > @@ -1135,7 +1135,13 @@ static int etm4_cpu_save(struct etmv4_drvdata *drvdata)
    > {
    > int i, ret = 0;
    > struct etmv4_save_state *state;
    > - struct device *etm_dev = &drvdata->csdev->dev;
    > + struct coresight_device *csdev = drvdata->csdev;
    > + struct device *etm_dev;
    > +
    > + if (WARN_ON(!csdev))
    > + return -ENODEV;
    > +
    > + etm_dev = &csdev->dev;
    >
    > /*
    > * As recommended by 3.4.1 ("The procedure when powering down the PE")
    > @@ -1261,6 +1267,10 @@ static void etm4_cpu_restore(struct etmv4_drvdata *drvdata)
    > {
    > int i;
    > struct etmv4_save_state *state = drvdata->save_state;
    > + struct coresight_device *csdev = drvdata->csdev;
    > +
    > + if (WARN_ON(!csdev))
    > + return;

    Restore and save operations are only called from etm4_cpu_pm_notify() where the
    check for a valid drvdata->csdev is already done.

    >
    > CS_UNLOCK(drvdata->base);
    >
    > @@ -1368,6 +1378,10 @@ static int etm4_cpu_pm_notify(struct notifier_block *nb, unsigned long cmd,
    >
    > drvdata = etmdrvdata[cpu];
    >
    > + /* If we have not registered the device there is nothing to do */
    > + if (!drvdata->csdev)
    > + return NOTIFY_OK;

    Can you describe the scenario you've seen this happening in? Probably best to
    add it to the changelog.

    > +
    > if (!drvdata->save_state)
    > return NOTIFY_OK;
    >
    > --
    > 2.24.1
    >

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