linux-kernel - Re: [PATCH] coresight: replicator: Reset replicator if context is lost

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Date:   Mon, 11 May 2020 21:56:43 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Coresight ML <coresight@...ts.linaro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] coresight: replicator: Reset replicator if context is
 lost

Hi Mathieu,

On 2020-05-11 21:49, Mathieu Poirier wrote:
> Hi Sai,
> 
> On Mon, 11 May 2020 at 02:34, Sai Prakash Ranjan
> <saiprakash.ranjan@...eaurora.org> wrote:
>> 
>> On some QCOM SoCs, replicators in Always-On domain loses its
>> context as soon as the clock is disabled. Currently as a part
>> of pm_runtime workqueue, clock is disabled after the replicator
>> is initialized by amba_pm_runtime_suspend assuming that context
>> is not lost which is not true for replicators with such
>> limitations. Hence check the replicator idfilter registers
>> in dynamic_replicator_enable() and reset again.
>> 
>> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
>> ---
>> 
>> More info here - https://lore.kernel.org/patchwork/patch/1231182/
>> 
>> ---
>>  drivers/hwtracing/coresight/coresight-replicator.c | 11 +++++++++++
>>  1 file changed, 11 insertions(+)
>> 
>> diff --git a/drivers/hwtracing/coresight/coresight-replicator.c 
>> b/drivers/hwtracing/coresight/coresight-replicator.c
>> index e7dc1c31d20d..11df63f51071 100644
>> --- a/drivers/hwtracing/coresight/coresight-replicator.c
>> +++ b/drivers/hwtracing/coresight/coresight-replicator.c
>> @@ -68,6 +68,17 @@ static int dynamic_replicator_enable(struct 
>> replicator_drvdata *drvdata,
>>         int rc = 0;
>>         u32 reg;
>> 
>> +       /*
>> +        * On some QCOM SoCs with replicators in Always-On domain, 
>> disabling
>> +        * clock will result in replicator losing its context. 
>> Currently
>> +        * as a part of pm_runtime workqueue, amba_pm_runtime_suspend 
>> disables
>> +        * clock assuming the context is not lost which is not true 
>> for cases
>> +        * with hardware limitations as the above.
>> +        */
>> +       if ((readl_relaxed(drvdata->base + REPLICATOR_IDFILTER0) == 0) 
>> &&
>> +           (readl_relaxed(drvdata->base + REPLICATOR_IDFILTER1) == 
>> 0))
>> +               dynamic_replicator_reset(drvdata);
>> +
> 
> Based on your comment here[1] and the ongoing conversation, I will
> wait for a V2.
> 
> Thanks,
> Mathieu
> 
> [1]. https://lkml.org/lkml/2020/5/11/650
> 

Yes, I will post a v2 once we have consensus regarding which way we need 
to
add a workaround for such QCOM SoCs.

Thanks,
Sai

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