Re: [PATCH V4 03/11] coresight: tmc: Extract device properties from AMBA pid based table lookup

[Suzuki K Poulose]

On 13/02/2024 03:13, Anshuman Khandual wrote:
> On 2/12/24 17:43, Suzuki K Poulose wrote:
> > On 23/01/2024 05:46, Anshuman Khandual wrote:
> > > This extracts device properties from AMBA pid based table lookup. This also
> > > defers tmc_etr_setup_caps() after the coresight device has been initialized
> > > so that PID value can be read.
> > >
> > > Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > > Cc: Mike Leach <mike.leach@xxxxxxxxxx>
> > > Cc: James Clark <james.clark@xxxxxxx>
> > > Cc: coresight@xxxxxxxxxxxxxxxx
> > > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > > Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> > > ---
> > >    .../hwtracing/coresight/coresight-tmc-core.c  | 19 +++++++++++++------
> > >    1 file changed, 13 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
> > > index 7ec5365e2b64..e71db3099a29 100644
> > > --- a/drivers/hwtracing/coresight/coresight-tmc-core.c
> > > +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
> > > @@ -370,16 +370,24 @@ static inline bool tmc_etr_has_non_secure_access(struct tmc_drvdata *drvdata)
> > >        return (auth & TMC_AUTH_NSID_MASK) == 0x3;
> > >    }
> > >    +#define TMC_AMBA_MASK 0xfffff
> > > +
> > > +static const struct amba_id tmc_ids[];
> > > +
> > >    /* Detect and initialise the capabilities of a TMC ETR */
> > > -static int tmc_etr_setup_caps(struct device *parent, u32 devid, void *dev_caps)
> > > +static int tmc_etr_setup_caps(struct device *parent, u32 devid)
> > >    {
> > >        int rc;
> > > -    u32 dma_mask = 0;
> > > +    u32 tmc_pid, dma_mask = 0;
> > >        struct tmc_drvdata *drvdata = dev_get_drvdata(parent);
> > > +    void *dev_caps;
> > >          if (!tmc_etr_has_non_secure_access(drvdata))
> > >            return -EACCES;
> > >    +    tmc_pid = coresight_get_pid(&drvdata->csdev->access) & TMC_AMBA_MASK;
> > > +    dev_caps = coresight_get_uci_data_from_amba(tmc_ids, tmc_pid);
> > > +
> > >        /* Set the unadvertised capabilities */
> > >        tmc_etr_init_caps(drvdata, (u32)(unsigned long)dev_caps);
> > >    @@ -497,10 +505,6 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
> > >            desc.type = CORESIGHT_DEV_TYPE_SINK;
> > >            desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_SYSMEM;
> > >            desc.ops = &tmc_etr_cs_ops;
> > > -        ret = tmc_etr_setup_caps(dev, devid,
> > > -                     coresight_get_uci_data(id));
> > > -        if (ret)
> > > -            goto out;
> > >            idr_init(&drvdata->idr);
> > >            mutex_init(&drvdata->idr_mutex);
> > >            dev_list = &etr_devs;
> > > @@ -539,6 +543,9 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
> > >            goto out;
> > >        }
> > >    +    if (drvdata->config_type == TMC_CONFIG_TYPE_ETR)
> > > +        ret = tmc_etr_setup_caps(dev, devid);
> > > +
> >
> > With this change, we silently accept an ETR that may only have "SECURE" access only and crash later while we try to enable tracing. You could
> > pass in the "access" (which is already in 'desc.access' in the original
> > call site and deal with it ?
>
> Just wondering, if something like the following will help ? A failed tmc_etr_setup_caps()
> because of failed tmc_etr_has_non_secure_access(), will unregister the coresight device
> before returning.
>
> --- a/drivers/hwtracing/coresight/coresight-tmc-core.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
> @@ -538,8 +538,13 @@ static int __tmc_probe(struct device *dev, struct resource *res)
>                  goto out;
>          }
>   
> -       if (drvdata->config_type == TMC_CONFIG_TYPE_ETR)
> +       if (drvdata->config_type == TMC_CONFIG_TYPE_ETR) {
>                  ret = tmc_etr_setup_caps(dev, devid);
> +               if (ret) {
> +                       coresight_unregister(drvdata->csdev);
> +                       goto out;
> +               }
> +       }

Why do we move the tmc_etr_setup_caps() in the first place ? We could 
retain where that was and pass "desc.access" parameter rather than 
registering the csdev and then relying csdev->access ?

Suzuki

>   
>          drvdata->miscdev.name = desc.name;
>          drvdata->miscdev.minor = MISC_DYNAMIC_MINOR;