Re: [PATCH v3 03/13] coresight: stm: Update STM driver to use Trace ID API

[Suzuki K Poulose]

On 06/10/2022 14:54, Mike Leach wrote:
> Hi Suzuki,
>
> On Mon, 3 Oct 2022 at 10:04, Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote:
> > On 09/08/2022 23:33, Mike Leach wrote:
> > > Updates the STM driver to use the trace ID allocation API.
> > > This uses the _system_id calls to allocate an ID on device poll,
> > > and release on device remove.
> > >
> > > The sysfs access to the STMTRACEIDR register has been changed from RW
> > > to RO. Having this value as writable is not appropriate for the new
> > > Trace ID scheme - and had potential to cause errors in the previous
> > > scheme if values clashed with other sources.
> > >
> > > Signed-off-by: Mike Leach <mike.leach@xxxxxxxxxx>
> > > Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>

> > > @@ -854,7 +830,7 @@ static void stm_init_generic_data(struct stm_drvdata *drvdata,
> > >
> > >    static int stm_probe(struct amba_device *adev, const struct amba_id *id)
> > >    {
> > > -     int ret;
> > > +     int ret, trace_id;
> > >        void __iomem *base;
> > >        struct device *dev = &adev->dev;
> > >        struct coresight_platform_data *pdata = NULL;
> > > @@ -938,12 +914,22 @@ static int stm_probe(struct amba_device *adev, const struct amba_id *id)
> > >                goto stm_unregister;
> > >        }
> > >
> > > +     trace_id = coresight_trace_id_get_system_id();
> > > +     if (trace_id < 0) {
> >
> > The above API returns "INVALID_ID" and not a negative error status.
> > I think it is better to fix the API to return:
> >
> >     ret < 0  - If there is any error
> >              - Otherwise a positive integer
> > And the users should be kept unaware of which ID is valid or invalid.
>
> coresight_trace_id_get_system_id() returns the ID if one can be
> allocated or -EINVAL if not.
>
> Not sure what you are looking at here.

Sorry, indeed I was mistaken there. It is the get_cpu_id() which
returns the INVALID_ID on failure. Please could we make that
consistent with this scheme ? i.e, < 0 on error.

Also, please could we add a comment above the exported functions
on their entry/exit criteria ? It is not clearly evident, unless
we follow the code and figure out.

Cheers
Suzuki