Re: [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@xxxxxxxxxxxxxx>
Tested-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
---
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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