[PATCH] arm64: dts: qcom: sdm845: Save Restore ETM Context - CoreSight

4 Aug 2020

Specify coresight-loses-context-with-cpu, making the ETM driver
to save the context on power-down.
While running system-wide tracing (-a) on DragonBoard845c, I hit the
following:
WARNING: CPU: 0 PID: 488 at drivers/hwtracing/coresight/coresight.c:209
 coresight_disclaim_device_unlocked+0x1c/0x38
 Modules linked in:
 CPU: 0 PID: 488 Comm: plain_perf Not tainted 5.8.0-rc6-34384-g9a3868dbef01 #6
 Hardware name: Thundercomm Dragonboard 845c (DT)
 pstate: 80400085 (Nzcv daIf +PAN -UAO BTYPE=--)
 pc : coresight_disclaim_device_unlocked+0x1c/0x38
 lr : etm4_disable_hw+0xb8/0xf0
 sp : ffff8000126139a0
 x29: ffff8000126139a0 x28: ffff0000e9c90000
 x27: ffff0000f158f180 x26: ffff0000f524d800
 x25: ffff0000fd6aba30 x24: 0000000000000004
 x23: ffff0000f158fa00 x22: ffff3aa88d4f9000
 x21: ffff0000f5196800 x20: ffff0000f524d800
 x19: ffff0000f524d080 x18: 0000000000000000
 x17: 0000000000000000 x16: 0000000000000000
 x15: 0000000000000000 x14: 0000000000000000
 x13: 0000000000000000 x12: 0000000000000000
 x11: 0000000000000000 x10: 0000000000000000
 x9 : ffffc5586ed1ef88 x8 : ffff0000e9c90000
 x7 : 00000000afa099e8 x6 : 00000000295ce537
 x5 : 0000000000000001 x4 : ffff8000105152a4
 x3 : 0000000000000001 x2 : ffff0000f524d1fc
 x1 : 0000000000000000 x0 : ffff800010515fa4
 Call trace:
  coresight_disclaim_device_unlocked+0x1c/0x38
  etm4_disable+0x5c/0xe0
  etm_event_stop+0xb4/0x128
  etm_event_del+0x1c/0x28
  event_sched_out.isra.0+0xbc/0x250
  group_sched_out.part.0+0x48/0xb8
  __perf_event_disable+0xec/0x258
  event_function+0xa4/0x130
  remote_function+0x64/0x78
  generic_exec_single+0xc4/0x150
  smp_call_function_single+0x178/0x208
  event_function_call+0x150/0x160
  _perf_event_disable+0x48/0x70
  perf_event_for_each_child+0x40/0x90
  _perf_ioctl+0x220/0x630
  perf_ioctl+0x50/0x80
  ksys_ioctl+0xb0/0xf0
  __arm64_sys_ioctl+0x28/0x38
  el0_svc_common.constprop.0+0x7c/0x198
  do_el0_svc+0x2c/0x98
  el0_sync_handler+0x9c/0x1b8
  el0_sync+0x158/0x180
This looks like due to ETM losing context with CPU power down
and thus losing the CLAIM tags, leading to an empty CLAIM tag set
while disabling the ETM.
Adding the "coresight-loses-context-with-cpu" property to the ETM
nodes fixes the issue.
Also the amount of trace collected is significantly larger
than without the patch.
Signed-off-by: Andrea Brunato andrea.brunato@arm.com
Suggested-by: Suzuki K Poulose suzuki.poulose@arm.com
---
PS: I experienced this on DragonBoard845c. I am not sure
if this issue persists on other board based on the sd845.
Sai, could you please share your thoughts?
---
 arch/arm64/boot/dts/qcom/sdm845.dtsi | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/sdm845.dtsi b/arch/arm64/boot/dts/qcom/sdm845.dtsi
index 8eb5a31346d2..42f5a08d8d34 100644
--- a/arch/arm64/boot/dts/qcom/sdm845.dtsi
+++ b/arch/arm64/boot/dts/qcom/sdm845.dtsi
@@ -2643,6 +2643,7 @@
clocks = <&aoss_qmp>;
    		clock-names = "apb_pclk";
+			arm,coresight-loses-context-with-cpu;
out-ports {
    			port {
@@ -2662,6 +2663,7 @@
clocks = <&aoss_qmp>;
    		clock-names = "apb_pclk";
+			arm,coresight-loses-context-with-cpu;
out-ports {
    			port {
@@ -2681,6 +2683,7 @@
clocks = <&aoss_qmp>;
    		clock-names = "apb_pclk";
+			arm,coresight-loses-context-with-cpu;
out-ports {
    			port {
@@ -2700,6 +2703,7 @@
clocks = <&aoss_qmp>;
    		clock-names = "apb_pclk";
+			arm,coresight-loses-context-with-cpu;
out-ports {
    			port {
@@ -2719,6 +2723,7 @@
clocks = <&aoss_qmp>;
    		clock-names = "apb_pclk";
+			arm,coresight-loses-context-with-cpu;
out-ports {
    			port {
@@ -2738,6 +2743,7 @@
clocks = <&aoss_qmp>;
    		clock-names = "apb_pclk";
+			arm,coresight-loses-context-with-cpu;
out-ports {
    			port {
@@ -2757,6 +2763,7 @@
clocks = <&aoss_qmp>;
    		clock-names = "apb_pclk";
+			arm,coresight-loses-context-with-cpu;
out-ports {
    			port {
@@ -2776,6 +2783,7 @@
clocks = <&aoss_qmp>;
    		clock-names = "apb_pclk";
+			arm,coresight-loses-context-with-cpu;
out-ports {
    			port {
-- 
2.17.1


    