[PATCH] firmware: qcom: tzmem: Use DO_ONCE_SLEEPABLE() in qcom_tzmem_enable()

[Mukesh Ojha]

qcom_tzmem_enable() is called from qcom_scm_probe() in a sleepable process
context. The helper it wraps, qcom_tzmem_init(), calls
qcom_scm_shm_bridge_enable() -> qcom_scm_call(), which invokes
might_sleep() and later acquires the qcom_scm_lock mutex via
__scm_smc_do().

DO_ONCE() takes the once_lock spinlock with IRQs disabled, so invoking
qcom_tzmem_init() from inside DO_ONCE() runs a sleepable call chain in
atomic context. CONFIG_DEBUG_ATOMIC_SLEEP=y catches this on boot:

  BUG: sleeping function called from invalid context at drivers/firmware/qcom/qcom_scm.c:334
  in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 49, name: kworker/u16:2
  ...
   __might_resched+0x148/0x24c
   __might_sleep+0x48/0x7c
   qcom_scm_call+0x30/0xc0
   __qcom_scm_is_call_available+0x98/0x100
   qcom_scm_shm_bridge_enable+0x60/0xbc
   qcom_tzmem_enable+0xf8/0x118
   qcom_scm_probe+0x2d0/0x680

  [ BUG: Invalid wait context ]
  ...
  kworker/u16:2/49 is trying to lock:
  ffffa83e8a485e38 (qcom_scm_lock){....}-{4:4}, at: __scm_smc_do+0x70/0x488

Switch to DO_ONCE_SLEEPABLE(), which guards the one-shot init with a
mutex-style path (__do_once_sleepable_start/done) that is safe to hold
across sleeping callees. All callers of qcom_tzmem_enable() are in
process context (driver probe), so this is safe.

Fixes: 9941fe8a04f3 ("firmware: qcom: scm: Fix tzmem state on probe retry")
Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Closes: https://lore.kernel.org/lkml/5ea74dd3-7471-4c7c-9242-c2005312b1ab@xxxxxxxxxxx/
Signed-off-by: Mukesh Ojha <mukesh.ojha@xxxxxxxxxxxxxxxx>
---
 drivers/firmware/qcom/qcom_tzmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/qcom/qcom_tzmem.c b/drivers/firmware/qcom/qcom_tzmem.c
index 0fd9581275f1..ebcdee3c5975 100644
--- a/drivers/firmware/qcom/qcom_tzmem.c
+++ b/drivers/firmware/qcom/qcom_tzmem.c
@@ -518,7 +518,7 @@ int qcom_tzmem_enable(struct device *dev)
 	static int result;
 
 	qcom_tzmem_dev = dev;
-	DO_ONCE(qcom_tzmem_do_init, &result);
+	DO_ONCE_SLEEPABLE(qcom_tzmem_do_init, &result);
 	return result;
 }
 EXPORT_SYMBOL_GPL(qcom_tzmem_enable);
-- 
2.53.0