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SubjectRe: [PATCH v2 1/3] coresight: cti: Prevent negative values of enable count
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Hi James,

Thanks for fixing this.

On 06/01/2023 15:23, James Clark wrote:
> Writing 0 to the enable control repeatedly results in a negative value
> for enable_req_count. After this, writing 1 to the enable control
> appears to not work until the count returns to positive.
>
> Change it so that it's impossible for enable_req_count to be < 0.

I prefer rephrasing the following :

> Returning an error will also allow us to decide whether to call
> runtime_pm_put() or not in the following commit.

"Return an error to indicate the disable request was invalid"

and don't mention the forward dependency.

>

May be also add ?

Fixes: 835d722ba10a ("coresight: cti: Initial CoreSight CTI Driver")

> Signed-off-by: James Clark <james.clark@arm.com>

Rest looks fine to me.

Suzuki


> ---
> drivers/hwtracing/coresight/coresight-cti-core.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-cti-core.c b/drivers/hwtracing/coresight/coresight-cti-core.c
> index d2cf4f4848e1..838872f2484d 100644
> --- a/drivers/hwtracing/coresight/coresight-cti-core.c
> +++ b/drivers/hwtracing/coresight/coresight-cti-core.c
> @@ -151,9 +151,16 @@ static int cti_disable_hw(struct cti_drvdata *drvdata)
> {
> struct cti_config *config = &drvdata->config;
> struct coresight_device *csdev = drvdata->csdev;
> + int ret = 0;
>
> spin_lock(&drvdata->spinlock);
>
> + /* don't allow negative refcounts, return an error */
> + if (!atomic_read(&drvdata->config.enable_req_count)) {
> + ret = -EINVAL;
> + goto cti_not_disabled;
> + }
> +
> /* check refcount - disable on 0 */
> if (atomic_dec_return(&drvdata->config.enable_req_count) > 0)
> goto cti_not_disabled;
> @@ -171,12 +178,12 @@ static int cti_disable_hw(struct cti_drvdata *drvdata)
> coresight_disclaim_device_unlocked(csdev);
> CS_LOCK(drvdata->base);
> spin_unlock(&drvdata->spinlock);
> - return 0;
> + return ret;
>
> /* not disabled this call */
> cti_not_disabled:
> spin_unlock(&drvdata->spinlock);
> - return 0;
> + return ret;
> }
>
> void cti_write_single_reg(struct cti_drvdata *drvdata, int offset, u32 value)

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