Re: [PATCH v4 3/3] firmware: qcom: scm: Fix tzmem state on probe retry

On Thu, Aug 06, 2026 at 04:42:09PM +0530, Mukesh Ojha wrote:
> On Thu, Aug 06, 2026 at 11:27:39AM +0200, Marek Szyprowski wrote:
> > On 24.07.2026 11:49, Mukesh Ojha wrote:
> > > qcom_tzmem_enable() returns -EBUSY if called a second time, but this
> > > causes probe retries to fail permanently if a later step in
> > > qcom_scm_probe() defers after qcom_tzmem_enable() has already succeeded.
> > >
> > > Use DO_ONCE() to ensure qcom_tzmem_init() runs exactly once across all
> > > calls in a thread-safe manner. qcom_tzmem_dev is set on every call since
> > > probe retries use the same device pointer. The result of the first
> > > initialisation is cached and returned to every subsequent caller.
> > >
> > > Fixes: 40289e35ca52 ("firmware: qcom: scm: enable the TZ mem allocator")
> > > Reviewed-by: Bartosz Golaszewski <[email protected]>
> > > Reviewed-by: Konrad Dybcio <[email protected]>
> > > Signed-off-by: Mukesh Ojha <[email protected]>
> > > ---
> > >  drivers/firmware/qcom/qcom_tzmem.c | 13 +++++++++----
> > >  1 file changed, 9 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/firmware/qcom/qcom_tzmem.c b/drivers/firmware/qcom/qcom_tzmem.c
> > > index 0635cbeacfc8..0fd9581275f1 100644
> > > --- a/drivers/firmware/qcom/qcom_tzmem.c
> > > +++ b/drivers/firmware/qcom/qcom_tzmem.c
> > > @@ -15,6 +15,7 @@
> > >  #include <linux/kernel.h>
> > >  #include <linux/list.h>
> > >  #include <linux/mm.h>
> > > +#include <linux/once.h>
> > >  #include <linux/radix-tree.h>
> > >  #include <linux/slab.h>
> > >  #include <linux/spinlock.h>
> > > @@ -507,14 +508,18 @@ phys_addr_t qcom_tzmem_to_phys(void *vaddr)
> > >  }
> > >  EXPORT_SYMBOL_GPL(qcom_tzmem_to_phys);
> > >  
> > > +static void qcom_tzmem_do_init(int *result)
> > > +{
> > > +	*result = qcom_tzmem_init();
> > > +}
> > > +
> > >  int qcom_tzmem_enable(struct device *dev)
> > >  {
> > > -	if (qcom_tzmem_dev)
> > > -		return -EBUSY;
> > > +	static int result;
> > >  
> > >  	qcom_tzmem_dev = dev;
> > > -
> > > -	return qcom_tzmem_init();
> > > +	DO_ONCE(qcom_tzmem_do_init, &result);
> > One should use DO_ONCE_SLEEPABLE() here, otherwise it triggers a warning during
> > boot on some on my test systems. Here is a log captured with
> > CONFIG_DEBUG_ATOMIC_SLEEP=y on recent linux-next releases, where this patch is
> > applied as commit 9941fe8a04f3 ("firmware: qcom: scm: Fix tzmem state on probe
> > retry"):
> 
> Thanks for reporting; I will spin a fix..and yes DO_ONCE_SLEEPABLE() is the right one.
>

Sent the change here https://lore.kernel.org/lkml/[email protected]/

-Mukesh