[PATCH] coresight: cti: Fix hang in cti_disable_hw()

[Suzuki K Poulose]

From: James Clark <james.clark at arm.com>

cti_enable_hw() and cti_disable_hw() are called from an atomic context
so shouldn't use runtime PM because it can result in a sleep when
communicating with firmware.

Since commit 3c6656337852 ("Revert "firmware: arm_scmi: Add clock
management to the SCMI power domain""), this causes a hang on Juno when
running the Perf Coresight tests or running this command:

  perf record -e cs_etm//u -- ls

This was also missed until the revert commit because pm_runtime_put()
was called with the wrong device until commit 692c9a499b28 ("coresight:
cti: Correct the parameter for pm_runtime_put")

With lock and scheduler debugging enabled the following is output:

   coresight cti_sys0: cti_enable_hw -- dev:cti_sys0  parent: 20020000.cti
   BUG: sleeping function called from invalid context at drivers/base/power/runtime.c:1151
   in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 330, name: perf-exec
   preempt_count: 2, expected: 0
   RCU nest depth: 0, expected: 0
   INFO: lockdep is turned off.
   irq event stamp: 0
   hardirqs last  enabled at (0): [<0000000000000000>] 0x0
   hardirqs last disabled at (0): [<ffff80000822b394>] copy_process+0xa0c/0x1948
   softirqs last  enabled at (0): [<ffff80000822b394>] copy_process+0xa0c/0x1948
   softirqs last disabled at (0): [<0000000000000000>] 0x0
   CPU: 3 PID: 330 Comm: perf-exec Not tainted 6.0.0-00053-g042116d99298 #7
   Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno Development Platform, BIOS EDK II Sep 13 2022
   Call trace:
    dump_backtrace+0x134/0x140
    show_stack+0x20/0x58
    dump_stack_lvl+0x8c/0xb8
    dump_stack+0x18/0x34
    __might_resched+0x180/0x228
    __might_sleep+0x50/0x88
    __pm_runtime_resume+0xac/0xb0
    cti_enable+0x44/0x120
    coresight_control_assoc_ectdev+0xc0/0x150
    coresight_enable_path+0xb4/0x288
    etm_event_start+0x138/0x170
    etm_event_add+0x48/0x70
    event_sched_in.isra.122+0xb4/0x280
    merge_sched_in+0x1fc/0x3d0
    visit_groups_merge.constprop.137+0x16c/0x4b0
    ctx_sched_in+0x114/0x1f0
    perf_event_sched_in+0x60/0x90
    ctx_resched+0x68/0xb0
    perf_event_exec+0x138/0x508
    begin_new_exec+0x52c/0xd40
    load_elf_binary+0x6b8/0x17d0
    bprm_execve+0x360/0x7f8
    do_execveat_common.isra.47+0x218/0x238
    __arm64_sys_execve+0x48/0x60
    invoke_syscall+0x4c/0x110
    el0_svc_common.constprop.4+0xfc/0x120
    do_el0_svc+0x34/0xc0
    el0_svc+0x40/0x98
    el0t_64_sync_handler+0x98/0xc0
    el0t_64_sync+0x170/0x174

Fix the issue by removing the runtime PM calls completely. They are not
needed here because it must have already been done when building the
path for a trace.

Fixes: 835d722ba10a ("coresight: cti: Initial CoreSight CTI Driver")
Reported-by: Aishwarya TCV <Aishwarya.TCV at arm.com>
Reported-by: Cristian Marussi <Cristian.Marussi at arm.com>
Suggested-by: Suzuki K Poulose <suzuki.poulose at arm.com>
Signed-off-by: James Clark <james.clark at arm.com>
Reviewed-by: Mike Leach <mike.leach at linaro.org>
Tested-by: Mike Leach <mike.leach at linaro.org>
[ Fix build warnings ]
Signed-off-by: Suzuki K Poulose <suzuki.poulose at arm.com>
---

Greg,
	Please could you apply this patch to your tree.
Thanks
Suzuki

Changes since previous posting:
  - Fix build warnings with 'unused variable'

---
 drivers/hwtracing/coresight/coresight-cti-core.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-cti-core.c b/drivers/hwtracing/coresight/coresight-cti-core.c
index 1be92342b5b9..c6e8c6542f24 100644
--- a/drivers/hwtracing/coresight/coresight-cti-core.c
+++ b/drivers/hwtracing/coresight/coresight-cti-core.c
@@ -90,11 +90,9 @@ void cti_write_all_hw_regs(struct cti_drvdata *drvdata)
 static int cti_enable_hw(struct cti_drvdata *drvdata)
 {
 	struct cti_config *config = &drvdata->config;
-	struct device *dev = &drvdata->csdev->dev;
 	unsigned long flags;
 	int rc = 0;
 
-	pm_runtime_get_sync(dev->parent);
 	spin_lock_irqsave(&drvdata->spinlock, flags);
 
 	/* no need to do anything if enabled or unpowered*/
@@ -119,7 +117,6 @@ static int cti_enable_hw(struct cti_drvdata *drvdata)
 	/* cannot enable due to error */
 cti_err_not_enabled:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
-	pm_runtime_put(dev->parent);
 	return rc;
 }
 
@@ -153,7 +150,6 @@ static void cti_cpuhp_enable_hw(struct cti_drvdata *drvdata)
 static int cti_disable_hw(struct cti_drvdata *drvdata)
 {
 	struct cti_config *config = &drvdata->config;
-	struct device *dev = &drvdata->csdev->dev;
 	struct coresight_device *csdev = drvdata->csdev;
 
 	spin_lock(&drvdata->spinlock);
@@ -175,7 +171,6 @@ static int cti_disable_hw(struct cti_drvdata *drvdata)
 	coresight_disclaim_device_unlocked(csdev);
 	CS_LOCK(drvdata->base);
 	spin_unlock(&drvdata->spinlock);
-	pm_runtime_put(dev->parent);
 	return 0;
 
 	/* not disabled this call */
-- 
2.37.3