Re: [PATCH v3 02/13] coresight: etb10: Fix handling of perf mode

Mathieu Poirier
2018-07-31T17:07:38Z

Hello,

On Thu, Jul 26, 2018 at 01:54:40PM +0100, Suzuki K Poulose wrote:
> If the ETB is already enabled in sysfs mode, the ETB reports
> success even if a perf mode is requested. Fix this by checking
> the requested mode.
>
> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
> drivers/hwtracing/coresight/coresight-etb10.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
> index 306119e..e5808fd 100644
> --- a/drivers/hwtracing/coresight/coresight-etb10.c
> +++ b/drivers/hwtracing/coresight/coresight-etb10.c
> @@ -148,8 +148,12 @@ static int etb_enable(struct coresight_device *csdev, u32 mode)
> return -EBUSY;
>
> /* Nothing to do, the tracer is already enabled. */
> - if (val == CS_MODE_SYSFS)
> - goto out;
> + if (val == CS_MODE_SYSFS) {
> + if (mode == CS_MODE_SYSFS)
> + goto out;
> + else
> + return -EBUSY;
> + }

How about:

if (val == CS_MODE_PERF)
return -EBUSY;

+ /* Don't let perf disturb sysFS sessions */
+ if (val == CS_MODE_SYSFS && mode = CS_MODE_PERF)
+ return -EBUSY;
+
/* Nothing to do, the tracer is already enabled. */
if (val == CS_MODE_SYSFS)
goto out;

I just find it more readable that way.

Thanks,
Mathieu

>
> spin_lock_irqsave(&drvdata->spinlock, flags);
> etb_enable_hw(drvdata);
> --
> 2.7.4
>