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

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Message-ID: <39c01eae-049b-4f5b-b86e-4af22c8246c1@arm.com>
Date: Tue, 13 Feb 2024 10:32:02 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Anshuman Khandual <anshuman.khandual@....com>,
 linux-arm-kernel@...ts.infradead.org
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Sudeep Holla <sudeep.holla@....com>, Mike Leach <mike.leach@...aro.org>,
 James Clark <james.clark@....com>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>, linux-acpi@...r.kernel.org,
 linux-kernel@...r.kernel.org, coresight@...ts.linaro.org,
 linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH V4 03/11] coresight: tmc: Extract device properties from
 AMBA pid based table lookup

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@....com>
>>> Cc: Mike Leach <mike.leach@...aro.org>
>>> Cc: James Clark <james.clark@....com>
>>> Cc: coresight@...ts.linaro.org
>>> Cc: linux-arm-kernel@...ts.infradead.org
>>> Cc: linux-kernel@...r.kernel.org
>>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>>> ---
>>>    .../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;