[PATCH] PM: opp: Fix NULL pointer exception on a v2 table combined with v1 opps

[Krzysztof Kozlowski]

dev_pm_opp_add() adds a v1 OPP.  If the Devicetree contains an OPP v2
table with required-opps, but the driver uses dev_pm_opp_add(), the
table might have required_opp_count!=0 but the opp->required_opps will
be NULL.  This leads to NULL pointer exception, e.g. with ufs-qcom.c
driver and v2 OPP table in DTS:

  Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
  ...
  Call trace:
   _required_opps_available+0x20/0x80
   _opp_add_v1+0xa8/0x110
   dev_pm_opp_add+0x54/0xcc
   ufshcd_async_scan+0x190/0x31c
   async_run_entry_fn+0x38/0x144

Fixes: cf65948d62c6 ("opp: Filter out OPPs based on availability of a required-OPP")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
---
 drivers/opp/core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 740407252298..d21b7e7e3f9f 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -1760,7 +1760,9 @@ int _opp_add(struct device *dev, struct dev_pm_opp *new_opp,
 	if (lazy_linking_pending(opp_table))
 		return 0;
 
-	_required_opps_available(new_opp, opp_table->required_opp_count);
+	/* No required_opps for v1 bindings OPP */
+	if (new_opp->required_opps)
+		_required_opps_available(new_opp, opp_table->required_opp_count);
 
 	return 0;
 }
-- 
2.32.0