Re: [PATCH 5/7] coresight: Clear self hosted claim tag on probe

[James Clark <james.clark@linaro.org>]

On 12/02/2025 6:24 pm, Mike Leach wrote:
> Hi James,
> 
> On Tue, 11 Feb 2025 at 10:40, James Clark <james.clark@linaro.org> wrote:
>>
>> This can be left behind from a crashed kernel after a kexec so clear it
>> when probing each device. Similarly to
>> coresight_disclaim_device_unlocked(), only clear it if it's already set
>> to avoid races with an external debugger.
>>
>> We need a csdev_access struct in etm_init_arch_data() so just replace
>> the iomem pointer with a full csdev_access struct. This means all usages
>> need to be updated to go through csa->base.
>>
>> Signed-off-by: James Clark <james.clark@linaro.org>
>> ---
>>   drivers/hwtracing/coresight/coresight-catu.c  |  1 +
>>   drivers/hwtracing/coresight/coresight-core.c  | 48 +++++++++++++++----
>>   .../hwtracing/coresight/coresight-cti-core.c  |  2 +
>>   drivers/hwtracing/coresight/coresight-etb10.c |  2 +
>>   drivers/hwtracing/coresight/coresight-etm.h   |  6 +--
>>   .../coresight/coresight-etm3x-core.c          | 28 +++++------
>>   .../coresight/coresight-etm3x-sysfs.c         |  8 ++--
>>   .../coresight/coresight-etm4x-core.c          |  2 +
>>   .../hwtracing/coresight/coresight-funnel.c    |  2 +
>>   .../coresight/coresight-replicator.c          |  1 +
>>   .../hwtracing/coresight/coresight-tmc-core.c  |  1 +
>>   include/linux/coresight.h                     |  3 ++
>>   12 files changed, 73 insertions(+), 31 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-catu.c b/drivers/hwtracing/coresight/coresight-catu.c
>> index d9259c0b6e64..575c2d247a90 100644
>> --- a/drivers/hwtracing/coresight/coresight-catu.c
>> +++ b/drivers/hwtracing/coresight/coresight-catu.c
>> @@ -558,6 +558,7 @@ static int __catu_probe(struct device *dev, struct resource *res)
>>          catu_desc.subtype.helper_subtype = CORESIGHT_DEV_SUBTYPE_HELPER_CATU;
>>          catu_desc.ops = &catu_ops;
>>
>> +       coresight_reset_claim(&catu_desc.access);
>>          drvdata->csdev = coresight_register(&catu_desc);
>>          if (IS_ERR(drvdata->csdev))
>>                  ret = PTR_ERR(drvdata->csdev);
>> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
>> index 7fe5d5d432c4..97f33ffad05e 100644
>> --- a/drivers/hwtracing/coresight/coresight-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-core.c
>> @@ -212,20 +212,48 @@ int coresight_claim_device(struct coresight_device *csdev)
>>   EXPORT_SYMBOL_GPL(coresight_claim_device);
>>
>>   /*
>> - * coresight_disclaim_device_unlocked : Clear the claim tag for the device.
>> + * Clear the claim tag for the device.
>> + * Returns an error if the device wasn't already claimed.
>> + */
>> +int coresight_reset_claim(struct csdev_access *csa)
> 
> Given the iusue being fixed - i.e. previous sessions having residual
> claims - and the fact that this funtion is only ever called from
> device initialisation as far as I can tell,
> would this be better to be called coresight_init_claim() and return /
> log an error only if the device _was_ actually claimed.
> 
> As it stands it seems to return an error if the device was not claimed
> - which on initialisation is the correct state!
> 
> Since the retrun code is ignored by all of the callees, the rerun
> could be dropped and a warning issued withing this function if the
> claim needed clearing.
> 

This is only to reuse code with coresight_disclaim_device_unlocked() 
which does use the return code. I can drop the return code from here but 
then we'd have to have two functions that do the same thing. One used on 
probe and the other used on disable.

>> +{
>> +       int ret;
>> +
>> +       CS_UNLOCK(csa->base);
>> +       ret = coresight_reset_claim_unlocked(csa);
>> +       CS_LOCK(csa->base);
>> +       return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(coresight_reset_claim);
>> +
>> +/*
>> + * Clear the claim tag for the device. Called with CS_UNLOCKed for the component.
>> + * Returns an error if the device wasn't already claimed.
>> + */
>> +int coresight_reset_claim_unlocked(struct csdev_access *csa)
> 
> Given the comment and the function - this could be named
> "coresight_clear_claim_unlocked()"
> 

I suppose we could rename it. It might cause some confusion with 
coresight_clear_self_claim_tag() though. I deliberately picked 'reset' 
because of when it was used on probe. Whereas 'clearing' is some 
existing function that only clears a bit without any extra logic. That 
kind of leaves it structured like this:

  clear: lowest level, only mechanical clear of the bit
  reset: clear if set, no warning
  disclaim: clear if set, warn if not set

> 
> Regards
> 
> Mike
> 
>> +{
>> +       if (coresight_read_claim_tags(csa) == CORESIGHT_CLAIM_SELF_HOSTED) {
>> +               coresight_clear_self_claim_tag(csa);
>> +               return 0;
>> +       }
>> +
>> +       return -EINVAL;
>> +}
>> +EXPORT_SYMBOL_GPL(coresight_reset_claim_unlocked);
>> +
>> +/*
>> + * coresight_disclaim_device_unlocked : Clear the claim tag for the device
>> + * and warn if the device wasn't already claimed.
>>    * Called with CS_UNLOCKed for the component.
>>    */
>>   void coresight_disclaim_device_unlocked(struct csdev_access *csa)
>>   {
>> -       if (coresight_read_claim_tags(csa) == CORESIGHT_CLAIM_SELF_HOSTED)
>> -               coresight_clear_self_claim_tag(csa);
>> -       else
>> -               /*
>> -                * The external agent may have not honoured our claim
>> -                * and has manipulated it. Or something else has seriously
>> -                * gone wrong in our driver.
>> -                */
>> -               WARN_ON_ONCE(1);
>> +       /*
>> +        * Warn if the external agent hasn't honoured our claim
>> +        * and has manipulated it. Or something else has seriously
>> +        * gone wrong in our driver.
>> +        */
>> +       WARN_ON_ONCE(coresight_reset_claim_unlocked(csa));
>>   }
>>   EXPORT_SYMBOL_GPL(coresight_disclaim_device_unlocked);
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-cti-core.c b/drivers/hwtracing/coresight/coresight-cti-core.c
>> index 073f67a41af9..389a72362f0c 100644
>> --- a/drivers/hwtracing/coresight/coresight-cti-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-cti-core.c
>> @@ -931,6 +931,8 @@ static int cti_probe(struct amba_device *adev, const struct amba_id *id)
>>          cti_desc.ops = &cti_ops;
>>          cti_desc.groups = drvdata->ctidev.con_groups;
>>          cti_desc.dev = dev;
>> +
>> +       coresight_reset_claim(&cti_desc.access);
>>          drvdata->csdev = coresight_register(&cti_desc);
>>          if (IS_ERR(drvdata->csdev)) {
>>                  ret = PTR_ERR(drvdata->csdev);
>> diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
>> index d8bc3e776c88..b598b2c0c9bb 100644
>> --- a/drivers/hwtracing/coresight/coresight-etb10.c
>> +++ b/drivers/hwtracing/coresight/coresight-etb10.c
>> @@ -772,6 +772,8 @@ static int etb_probe(struct amba_device *adev, const struct amba_id *id)
>>          desc.pdata = pdata;
>>          desc.dev = dev;
>>          desc.groups = coresight_etb_groups;
>> +
>> +       coresight_reset_claim(&desc.access);
>>          drvdata->csdev = coresight_register(&desc);
>>          if (IS_ERR(drvdata->csdev))
>>                  return PTR_ERR(drvdata->csdev);
>> diff --git a/drivers/hwtracing/coresight/coresight-etm.h b/drivers/hwtracing/coresight/coresight-etm.h
>> index e02c3ea972c9..a89736309c27 100644
>> --- a/drivers/hwtracing/coresight/coresight-etm.h
>> +++ b/drivers/hwtracing/coresight/coresight-etm.h
>> @@ -229,7 +229,7 @@ struct etm_config {
>>    * @config:    structure holding configuration parameters.
>>    */
>>   struct etm_drvdata {
>> -       void __iomem                    *base;
>> +       struct csdev_access             csa;
>>          struct clk                      *atclk;
>>          struct coresight_device         *csdev;
>>          spinlock_t                      spinlock;
>> @@ -260,7 +260,7 @@ static inline void etm_writel(struct etm_drvdata *drvdata,
>>                                  "invalid CP14 access to ETM reg: %#x", off);
>>                  }
>>          } else {
>> -               writel_relaxed(val, drvdata->base + off);
>> +               writel_relaxed(val, drvdata->csa.base + off);
>>          }
>>   }
>>
>> @@ -274,7 +274,7 @@ static inline unsigned int etm_readl(struct etm_drvdata *drvdata, u32 off)
>>                                  "invalid CP14 access to ETM reg: %#x", off);
>>                  }
>>          } else {
>> -               val = readl_relaxed(drvdata->base + off);
>> +               val = readl_relaxed(drvdata->csa.base + off);
>>          }
>>
>>          return val;
>> diff --git a/drivers/hwtracing/coresight/coresight-etm3x-core.c b/drivers/hwtracing/coresight/coresight-etm3x-core.c
>> index 509f53b69e42..0b010683b883 100644
>> --- a/drivers/hwtracing/coresight/coresight-etm3x-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-etm3x-core.c
>> @@ -86,9 +86,9 @@ static void etm_set_pwrup(struct etm_drvdata *drvdata)
>>   {
>>          u32 etmpdcr;
>>
>> -       etmpdcr = readl_relaxed(drvdata->base + ETMPDCR);
>> +       etmpdcr = readl_relaxed(drvdata->csa.base + ETMPDCR);
>>          etmpdcr |= ETMPDCR_PWD_UP;
>> -       writel_relaxed(etmpdcr, drvdata->base + ETMPDCR);
>> +       writel_relaxed(etmpdcr, drvdata->csa.base + ETMPDCR);
>>          /* Ensure pwrup completes before subsequent cp14 accesses */
>>          mb();
>>          isb();
>> @@ -101,9 +101,9 @@ static void etm_clr_pwrup(struct etm_drvdata *drvdata)
>>          /* Ensure pending cp14 accesses complete before clearing pwrup */
>>          mb();
>>          isb();
>> -       etmpdcr = readl_relaxed(drvdata->base + ETMPDCR);
>> +       etmpdcr = readl_relaxed(drvdata->csa.base + ETMPDCR);
>>          etmpdcr &= ~ETMPDCR_PWD_UP;
>> -       writel_relaxed(etmpdcr, drvdata->base + ETMPDCR);
>> +       writel_relaxed(etmpdcr, drvdata->csa.base + ETMPDCR);
>>   }
>>
>>   /**
>> @@ -365,7 +365,7 @@ static int etm_enable_hw(struct etm_drvdata *drvdata)
>>          struct etm_config *config = &drvdata->config;
>>          struct coresight_device *csdev = drvdata->csdev;
>>
>> -       CS_UNLOCK(drvdata->base);
>> +       CS_UNLOCK(drvdata->csa.base);
>>
>>          rc = coresight_claim_device_unlocked(csdev);
>>          if (rc)
>> @@ -427,7 +427,7 @@ static int etm_enable_hw(struct etm_drvdata *drvdata)
>>          etm_clr_prog(drvdata);
>>
>>   done:
>> -       CS_LOCK(drvdata->base);
>> +       CS_LOCK(drvdata->csa.base);
>>
>>          dev_dbg(&drvdata->csdev->dev, "cpu: %d enable smp call done: %d\n",
>>                  drvdata->cpu, rc);
>> @@ -589,7 +589,7 @@ static void etm_disable_hw(void *info)
>>          struct etm_config *config = &drvdata->config;
>>          struct coresight_device *csdev = drvdata->csdev;
>>
>> -       CS_UNLOCK(drvdata->base);
>> +       CS_UNLOCK(drvdata->csa.base);
>>          etm_set_prog(drvdata);
>>
>>          /* Read back sequencer and counters for post trace analysis */
>> @@ -601,7 +601,7 @@ static void etm_disable_hw(void *info)
>>          etm_set_pwrdwn(drvdata);
>>          coresight_disclaim_device_unlocked(&csdev->access);
>>
>> -       CS_LOCK(drvdata->base);
>> +       CS_LOCK(drvdata->csa.base);
>>
>>          dev_dbg(&drvdata->csdev->dev,
>>                  "cpu: %d disable smp call done\n", drvdata->cpu);
>> @@ -614,7 +614,7 @@ static void etm_disable_perf(struct coresight_device *csdev)
>>          if (WARN_ON_ONCE(drvdata->cpu != smp_processor_id()))
>>                  return;
>>
>> -       CS_UNLOCK(drvdata->base);
>> +       CS_UNLOCK(drvdata->csa.base);
>>
>>          /* Setting the prog bit disables tracing immediately */
>>          etm_set_prog(drvdata);
>> @@ -626,7 +626,7 @@ static void etm_disable_perf(struct coresight_device *csdev)
>>          etm_set_pwrdwn(drvdata);
>>          coresight_disclaim_device_unlocked(&csdev->access);
>>
>> -       CS_LOCK(drvdata->base);
>> +       CS_LOCK(drvdata->csa.base);
>>
>>          /*
>>           * perf will release trace ids when _free_aux()
>> @@ -772,7 +772,7 @@ static void etm_init_arch_data(void *info)
>>          /* Make sure all registers are accessible */
>>          etm_os_unlock(drvdata);
>>
>> -       CS_UNLOCK(drvdata->base);
>> +       CS_UNLOCK(drvdata->csa.base);
>>
>>          /* First dummy read */
>>          (void)etm_readl(drvdata, ETMPDSR);
>> @@ -803,9 +803,10 @@ static void etm_init_arch_data(void *info)
>>          drvdata->nr_ext_out = BMVAL(etmccr, 20, 22);
>>          drvdata->nr_ctxid_cmp = BMVAL(etmccr, 24, 25);
>>
>> +       coresight_reset_claim_unlocked(&drvdata->csa);
>>          etm_set_pwrdwn(drvdata);
>>          etm_clr_pwrup(drvdata);
>> -       CS_LOCK(drvdata->base);
>> +       CS_LOCK(drvdata->csa.base);
>>   }
>>
>>   static int __init etm_hp_setup(void)
>> @@ -866,8 +867,7 @@ static int etm_probe(struct amba_device *adev, const struct amba_id *id)
>>          if (IS_ERR(base))
>>                  return PTR_ERR(base);
>>
>> -       drvdata->base = base;
>> -       desc.access = CSDEV_ACCESS_IOMEM(base);
>> +       desc.access = drvdata->csa = CSDEV_ACCESS_IOMEM(base);
>>
>>          spin_lock_init(&drvdata->spinlock);
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
>> index 68c644be9813..af566b62785c 100644
>> --- a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
>> +++ b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
>> @@ -50,11 +50,11 @@ static ssize_t etmsr_show(struct device *dev,
>>
>>          pm_runtime_get_sync(dev->parent);
>>          spin_lock_irqsave(&drvdata->spinlock, flags);
>> -       CS_UNLOCK(drvdata->base);
>> +       CS_UNLOCK(drvdata->csa.base);
>>
>>          val = etm_readl(drvdata, ETMSR);
>>
>> -       CS_LOCK(drvdata->base);
>> +       CS_LOCK(drvdata->csa.base);
>>          spin_unlock_irqrestore(&drvdata->spinlock, flags);
>>          pm_runtime_put(dev->parent);
>>
>> @@ -949,9 +949,9 @@ static ssize_t seq_curr_state_show(struct device *dev,
>>          pm_runtime_get_sync(dev->parent);
>>          spin_lock_irqsave(&drvdata->spinlock, flags);
>>
>> -       CS_UNLOCK(drvdata->base);
>> +       CS_UNLOCK(drvdata->csa.base);
>>          val = (etm_readl(drvdata, ETMSQR) & ETM_SQR_MASK);
>> -       CS_LOCK(drvdata->base);
>> +       CS_LOCK(drvdata->csa.base);
>>
>>          spin_unlock_irqrestore(&drvdata->spinlock, flags);
>>          pm_runtime_put(dev->parent);
>> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
>> index 45b30a4b3eba..3609bb74c4ec 100644
>> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
>> @@ -1337,6 +1337,8 @@ static void etm4_init_arch_data(void *info)
>>          drvdata->nrseqstate = FIELD_GET(TRCIDR5_NUMSEQSTATE_MASK, etmidr5);
>>          /* NUMCNTR, bits[30:28] number of counters available for tracing */
>>          drvdata->nr_cntr = FIELD_GET(TRCIDR5_NUMCNTR_MASK, etmidr5);
>> +
>> +       coresight_reset_claim_unlocked(csa);
>>          etm4_cs_lock(drvdata, csa);
>>          cpu_detect_trace_filtering(drvdata);
>>   }
>> diff --git a/drivers/hwtracing/coresight/coresight-funnel.c b/drivers/hwtracing/coresight/coresight-funnel.c
>> index e986922d555b..be2a47636ef3 100644
>> --- a/drivers/hwtracing/coresight/coresight-funnel.c
>> +++ b/drivers/hwtracing/coresight/coresight-funnel.c
>> @@ -255,6 +255,7 @@ static int funnel_probe(struct device *dev, struct resource *res)
>>                  drvdata->base = base;
>>                  desc.groups = coresight_funnel_groups;
>>                  desc.access = CSDEV_ACCESS_IOMEM(base);
>> +               coresight_reset_claim(&desc.access);
>>          }
>>
>>          dev_set_drvdata(dev, drvdata);
>> @@ -272,6 +273,7 @@ static int funnel_probe(struct device *dev, struct resource *res)
>>          desc.ops = &funnel_cs_ops;
>>          desc.pdata = pdata;
>>          desc.dev = dev;
>> +
>>          drvdata->csdev = coresight_register(&desc);
>>          if (IS_ERR(drvdata->csdev)) {
>>                  ret = PTR_ERR(drvdata->csdev);
>> diff --git a/drivers/hwtracing/coresight/coresight-replicator.c b/drivers/hwtracing/coresight/coresight-replicator.c
>> index 5d42a9a8c460..679a36effbe8 100644
>> --- a/drivers/hwtracing/coresight/coresight-replicator.c
>> +++ b/drivers/hwtracing/coresight/coresight-replicator.c
>> @@ -284,6 +284,7 @@ static int replicator_probe(struct device *dev, struct resource *res)
>>          desc.pdata = dev->platform_data;
>>          desc.dev = dev;
>>
>> +       coresight_reset_claim(&desc.access);
>>          drvdata->csdev = coresight_register(&desc);
>>          if (IS_ERR(drvdata->csdev)) {
>>                  ret = PTR_ERR(drvdata->csdev);
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
>> index e9876252a789..5ac4e3c706ac 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
>> @@ -558,6 +558,7 @@ static int __tmc_probe(struct device *dev, struct resource *res)
>>          dev->platform_data = pdata;
>>          desc.pdata = pdata;
>>
>> +       coresight_reset_claim(&desc.access);
>>          drvdata->csdev = coresight_register(&desc);
>>          if (IS_ERR(drvdata->csdev)) {
>>                  ret = PTR_ERR(drvdata->csdev);
>> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
>> index 937931d107e0..11808aee9d1d 100644
>> --- a/include/linux/coresight.h
>> +++ b/include/linux/coresight.h
>> @@ -655,6 +655,9 @@ extern int coresight_claim_device_unlocked(struct coresight_device *csdev);
>>
>>   extern void coresight_disclaim_device(struct csdev_access *csa);
>>   extern void coresight_disclaim_device_unlocked(struct csdev_access *csa);
>> +int coresight_reset_claim_unlocked(struct csdev_access *csa);
>> +int coresight_reset_claim(struct csdev_access *csa);
>> +
>>   extern char *coresight_alloc_device_name(struct coresight_dev_list *devs,
>>                                           struct device *dev);
>>
>> --
>> 2.34.1
>>
> 
>