[PATCH 0/2] Fix two issues in ptp_s390 driver

[PATCH 0/2] Fix two issues in ptp_s390 driver

[Sven Schnelle]

This patchset fixes two issues in the ptp_s390 driver:

a) Missing check of condition code in qpt query function. When PTFF QPT is
   not supported ptp_s390_qpt_gettime() would just return without storing
   the physical time.

b) Missing test for presence of facility 28 during driver registration.

Sven Schnelle (2):
  ptp: ptp_s390: Add missing CC check for ptff()
  ptp: ptp_s390: Add missing facility check

 drivers/ptp/ptp_s390.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

-- 
2.53.0

[PATCH 1/2] ptp: ptp_s390: Add missing CC check for ptff()

[Sven Schnelle]

The code doesn't honor the returned condition code when issuing
the PTFF_QPT call. Fix this by checking the return code and returning
EIO if it is not zero.

Fixes: 2d7de7a3010d ("s390/time: Add PtP driver")
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Cc: stable@kernel.org
---
 drivers/ptp/ptp_s390.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/ptp/ptp_s390.c b/drivers/ptp/ptp_s390.c
index 29618eb9bf44..7299c3aae65f 100644
--- a/drivers/ptp/ptp_s390.c
+++ b/drivers/ptp/ptp_s390.c
@@ -48,7 +48,8 @@ static int ptp_s390_qpt_gettime(struct ptp_clock_info *ptp,
 {
 	unsigned long tod;
 
-	ptff(&tod, sizeof(tod), PTFF_QPT);
+	if (ptff(&tod, sizeof(tod), PTFF_QPT) != 0)
+		return -EOPNOTSUPP;
 	*ts = tod_to_timespec64(tod);
 	return 0;
 }
-- 
2.53.0

[PATCH 2/2] ptp: ptp_s390: Add missing facility check

[Sven Schnelle]

Only register the physical clock when facility 28 is installed.

Fixes: 2d7de7a3010d ("s390/time: Add PtP driver")
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Cc: stable@kernel.org
---
 drivers/ptp/ptp_s390.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/ptp/ptp_s390.c b/drivers/ptp/ptp_s390.c
index 7299c3aae65f..3ea94648cdde 100644
--- a/drivers/ptp/ptp_s390.c
+++ b/drivers/ptp/ptp_s390.c
@@ -108,6 +108,9 @@ static __init int ptp_s390_init(void)
 	if (IS_ERR(ptp_stcke_clock))
 		return PTR_ERR(ptp_stcke_clock);
 
+	if (!test_facility(28))
+		return 0;
+
 	ptp_qpt_clock = ptp_clock_register(&ptp_s390_qpt_info, NULL);
 	if (IS_ERR(ptp_qpt_clock)) {
 		ptp_clock_unregister(ptp_stcke_clock);
@@ -118,7 +121,8 @@ static __init int ptp_s390_init(void)
 
 static __exit void ptp_s390_exit(void)
 {
-	ptp_clock_unregister(ptp_qpt_clock);
+	if (ptp_qpt_clock)
+		ptp_clock_unregister(ptp_qpt_clock);
 	ptp_clock_unregister(ptp_stcke_clock);
 }
 
-- 
2.53.0

Re: [PATCH 2/2] ptp: ptp_s390: Add missing facility check

[Heiko Carstens]

On Tue, Jul 14, 2026 at 10:49:21AM +0200, Sven Schnelle wrote:
> Only register the physical clock when facility 28 is installed.
> 
> Fixes: 2d7de7a3010d ("s390/time: Add PtP driver")
> Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
> Cc: stable@kernel.org
> ---
>  drivers/ptp/ptp_s390.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ptp/ptp_s390.c b/drivers/ptp/ptp_s390.c
> index 7299c3aae65f..3ea94648cdde 100644
> --- a/drivers/ptp/ptp_s390.c
> +++ b/drivers/ptp/ptp_s390.c
> @@ -108,6 +108,9 @@ static __init int ptp_s390_init(void)
>  	if (IS_ERR(ptp_stcke_clock))
>  		return PTR_ERR(ptp_stcke_clock);
>  
> +	if (!test_facility(28))
> +		return 0;
> +
>  	ptp_qpt_clock = ptp_clock_register(&ptp_s390_qpt_info, NULL);
>  	if (IS_ERR(ptp_qpt_clock)) {
>  		ptp_clock_unregister(ptp_stcke_clock);

Wouldn't it make more sense to check if PTFF-QPT is available via PTFF-QAF
before registering the clock? This would also avoid the need of the first
patch - since then it is guaranteed that PTFF-QPT will always return with
condition code zero.

And... we wouldn't have the potential oddity to have a clock registered which
doesn't work.