linux-kernel - Re: [PATCH 2/2] coresight: tmc: Add shutdown callback for TMC ETR/ETF

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Message-ID: <f3c3a52effa9828d47712a9d4f852dfc@codeaurora.org>
Date:   Mon, 01 Jun 2020 22:45:09 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Mike Leach <mike.leach@...aro.org>
Cc:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org,
        Coresight ML <coresight@...ts.linaro.org>,
        Stephen Boyd <swboyd@...omium.org>
Subject: Re: [PATCH 2/2] coresight: tmc: Add shutdown callback for TMC ETR/ETF

Hi Mike,

Thanks for the review.

On 2020-06-01 19:05, Mike Leach wrote:
> Hi,
> 
> On Mon, 1 Jun 2020 at 09:02, Sai Prakash Ranjan
> <saiprakash.ranjan@...eaurora.org> wrote:
>> 
>> Implement a shutdown callback to ensure ETR/ETF hardware is
>> properly shutdown in reboot/shutdown path. This is required
>> for ETR/ETF which has SMMU address translation enabled like
>> on SC7180 SoC and few others. If the hardware is still accessing
>> memory after SMMU translation is disabled as part of SMMU
>> shutdown callback in system reboot or shutdown path, then
>> IOVAs(I/O virtual address) which it was using will go on the bus
>> as the physical addresses which might result in unknown crashes
>> (NoC/interconnect errors). So we make sure from this shutdown
>> callback that the ETR/ETF is shutdown before SMMU translation is
>> disabled and device_link in SMMU driver will take care of ordering
>> of shutdown callbacks such that SMMU shutdown callback is not
>> called before any of its consumer shutdown callbacks.
>> 
>> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
>> ---
>>  .../hwtracing/coresight/coresight-tmc-etf.c   |  4 +--
>>  .../hwtracing/coresight/coresight-tmc-etr.c   |  2 +-
>>  drivers/hwtracing/coresight/coresight-tmc.c   | 29 
>> +++++++++++++++++++
>>  drivers/hwtracing/coresight/coresight-tmc.h   |  3 ++
>>  4 files changed, 35 insertions(+), 3 deletions(-)
>> 
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c 
>> b/drivers/hwtracing/coresight/coresight-tmc-etf.c
>> index 36cce2bfb744..cba3e7592820 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
>> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
>> @@ -85,7 +85,7 @@ static void __tmc_etb_disable_hw(struct tmc_drvdata 
>> *drvdata)
>>         CS_LOCK(drvdata->base);
>>  }
>> 
>> -static void tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
>> +void tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
>>  {
>>         __tmc_etb_disable_hw(drvdata);
>>         coresight_disclaim_device(drvdata->base);
>> @@ -118,7 +118,7 @@ static int tmc_etf_enable_hw(struct tmc_drvdata 
>> *drvdata)
>>         return 0;
>>  }
>> 
>> -static void tmc_etf_disable_hw(struct tmc_drvdata *drvdata)
>> +void tmc_etf_disable_hw(struct tmc_drvdata *drvdata)
>>  {
>>         CS_UNLOCK(drvdata->base);
>> 
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c 
>> b/drivers/hwtracing/coresight/coresight-tmc-etr.c
>> index 625882bc8b08..b29c2db94d96 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
>> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
>> @@ -1110,7 +1110,7 @@ static void __tmc_etr_disable_hw(struct 
>> tmc_drvdata *drvdata)
>> 
>>  }
>> 
>> -static void tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
>> +void tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
>>  {
>>         __tmc_etr_disable_hw(drvdata);
>>         /* Disable CATU device if this ETR is connected to one */
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc.c 
>> b/drivers/hwtracing/coresight/coresight-tmc.c
>> index 5a271ebc4585..7e687a356fe0 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc.c
>> +++ b/drivers/hwtracing/coresight/coresight-tmc.c
>> @@ -540,6 +540,34 @@ static int tmc_probe(struct amba_device *adev, 
>> const struct amba_id *id)
>>         return ret;
>>  }
>> 
>> +static void tmc_shutdown(struct amba_device *adev)
>> +{
>> +       struct tmc_drvdata *drvdata = amba_get_drvdata(adev);
>> +
> 
> Take drvdata->spinlock here? The tmc_xxx_disable_hw functions are
> normally called with the spinlock claimed.
> 

Sure will take spinlock here.

>> +       if (!drvdata->enable)
> 
> As per previous patch drvdata->mode can be used here.
> 

Yes, will use mode here and drop enable flag in the next version.

Thanks,
Sai

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