linux-kernel - Re: [RFC PATCH] coresight: dynamic-replicator: Fix handling of multiple connections

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Message-ID: <CAJ9a7VgQzK1XSCvLwuqODwkWfvo=6Wwps7Db+pL5xYDeCuktrg@mail.gmail.com>
Date:   Mon, 6 Apr 2020 11:55:21 +0100
From:   Mike Leach <mike.leach@...aro.org>
To:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Cc:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Leo Yan <leo.yan@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Stephen Boyd <swboyd@...omium.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [RFC PATCH] coresight: dynamic-replicator: Fix handling of
 multiple connections

Hi,

The programmable replicator hardware by design enables trace through
both ports on reset. (see 1, section 4.4, 9.11)  The replicator driver
overrides this functionality to disable output, until the Coresight
infrastructure chooses a path from source to sink.
Now given that the hardware design is such that we must be able to
allow trace to be sent to both ports, a generic patch to prevent this
does not seem appropriate here.

I think this needs further investigation - to determine why this
appears to be failing in this particular instance.

Regards

Mike

[1] CoreSight System-on-Chip SoC-600 TRM, r3p2, 100806_0302_00_en

On Sun, 5 Apr 2020 at 11:28, Sai Prakash Ranjan
<saiprakash.ranjan@...eaurora.org> wrote:
>
> Since commit 30af4fb619e5 ("coresight: dynamic-replicator:
> Handle multiple connections"), we do not make sure that
> the other port is disabled when the dynamic replicator is
> enabled. This is seen to cause the CPU hardlockup atleast
> on SC7180 SoC when enabling ETM with ETR as the sink via
> sysfs.
>
>   Kernel panic - not syncing: Watchdog detected hard LOCKUP on cpu 0
>   CPU: 7 PID: 0 Comm: swapper/7 Tainted: G S  B             5.4.25 #100
>   Hardware name: Qualcomm Technologies, Inc. SC7180 IDP (DT)
>   Call trace:
>    dump_backtrace+0x0/0x188
>    show_stack+0x20/0x2c
>    dump_stack+0xdc/0x144
>    panic+0x168/0x370
>    arch_seccomp_spec_mitigate+0x0/0x14
>    watchdog_timer_fn+0x68/0x290
>    __hrtimer_run_queues+0x264/0x498
>    hrtimer_interrupt+0xf0/0x22c
>    arch_timer_handler_phys+0x40/0x50
>    handle_percpu_devid_irq+0x8c/0x158
>    __handle_domain_irq+0x84/0xc4
>    gic_handle_irq+0x100/0x1c4
>    el1_irq+0xbc/0x180
>    arch_cpu_idle+0x3c/0x5c
>    default_idle_call+0x1c/0x38
>    do_idle+0x100/0x280
>    cpu_startup_entry+0x24/0x28
>    secondary_start_kernel+0x15c/0x170
>   SMP: stopping secondary CPUs
>
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
> ---
>  .../hwtracing/coresight/coresight-replicator.c    | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-replicator.c b/drivers/hwtracing/coresight/coresight-replicator.c
> index e7dc1c31d20d..f4eaa38f8f43 100644
> --- a/drivers/hwtracing/coresight/coresight-replicator.c
> +++ b/drivers/hwtracing/coresight/coresight-replicator.c
> @@ -66,14 +66,16 @@ static int dynamic_replicator_enable(struct replicator_drvdata *drvdata,
>                                      int inport, int outport)
>  {
>         int rc = 0;
> -       u32 reg;
> +       u32 reg0, reg1;
>
>         switch (outport) {
>         case 0:
> -               reg = REPLICATOR_IDFILTER0;
> +               reg0 = REPLICATOR_IDFILTER0;
> +               reg1 = REPLICATOR_IDFILTER1;
>                 break;
>         case 1:
> -               reg = REPLICATOR_IDFILTER1;
> +               reg0 = REPLICATOR_IDFILTER1;
> +               reg1 = REPLICATOR_IDFILTER0;
>                 break;
>         default:
>                 WARN_ON(1);
> @@ -87,8 +89,11 @@ static int dynamic_replicator_enable(struct replicator_drvdata *drvdata,
>                 rc = coresight_claim_device_unlocked(drvdata->base);
>
>         /* Ensure that the outport is enabled. */
> -       if (!rc)
> -               writel_relaxed(0x00, drvdata->base + reg);
> +       if (!rc) {
> +               writel_relaxed(0x00, drvdata->base + reg0);
> +               writel_relaxed(0xff, drvdata->base + reg1);
> +       }
> +
>         CS_LOCK(drvdata->base);
>
>         return rc;
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation



-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK