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SubjectRe: [PATCH] coresight: dynamic-replicator: Fix handling of multiple connections
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On 04/26/2020 03:37 PM, Sai Prakash Ranjan 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 with the following topology when enabling ETM
> with ETR as the sink via sysfs. Since there is no trace id
> logic in coresight yet to make use of multiple sinks in
> parallel for different trace sessions, disable the other
> port when one port is turned on.
>
> etm0_out
> |
> apss_funnel_in0
> |
> apss_merge_funnel_in
> |
> funnel1_in4
> |
> merge_funnel_in1
> |
> swao_funnel_in
> |
> etf_in
> |
> swao_replicator_in
> |
> replicator_in
> |
> etr_in
>
> 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@codeaurora.org>
> Tested-by: Stephen Boyd <swboyd@chromium.org>
> ---
> Changes since RFC:
> * Reworded commit text and included the topology on SC7180.


> ---
> .../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);
> + }
> +

This is not sufficient. You must prevent another session trying to
enable the other port of the replicator as this could silently fail
the "on-going" session. Not ideal. Fail the attempt to enable a port
if the other port is active. You could track this in software and
fail early.

Suzuki

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