2023-01-10 11:31:52

by James Clark

Subject: [PATCH v3 1/3] coresight: cti: Prevent negative values of enable count

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.
Return an error to indicate that the disable request was invalid.

Fixes: 835d722ba10a ("coresight: cti: Initial CoreSight CTI Driver")
Tested-by: Jinlong Mao <[email protected]>
Signed-off-by: James Clark <[email protected]>
---
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)
--
2.25.1

2023-01-12 15:23:58

by Mike Leach

Subject: Re: [PATCH v3 1/3] coresight: cti: Prevent negative values of enable count

On Tue, 10 Jan 2023 at 11:08, James Clark <[email protected]> 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.
> Return an error to indicate that the disable request was invalid.
>
> Fixes: 835d722ba10a ("coresight: cti: Initial CoreSight CTI Driver")
> Tested-by: Jinlong Mao <[email protected]>
> Signed-off-by: James Clark <[email protected]>
> ---
> 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)
> --
> 2.25.1
>

reviewed-by: Mike Leach <[email protected]>
--
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK