[PATCH v2] iommu/rockchip: make clock handling optional

[Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>]

iommu clocks are optional, so the driver should not fail if they are not
present. Instead just set the number of clocks to 0, which the clk-blk APIs
can handle just fine.

Fixes: f2e3a5f557ad ("iommu/rockchip: Control clocks needed to access the IOMMU")
Signed-off-by: Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>
Reviewed-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
---
changes in v2:
- keep it required in the binding for future variants
  but optional in the code for backwards compatiblity
- follow Robin Murphy's beautification suggestion

As the original changes breaks a lot of display support in 4.17-rc1,
this should abviously go in as fix into 4.17.

 drivers/iommu/rockchip-iommu.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
index 5fc8656c60f9..422d22990289 100644
--- a/drivers/iommu/rockchip-iommu.c
+++ b/drivers/iommu/rockchip-iommu.c
@@ -1175,8 +1175,15 @@ static int rk_iommu_probe(struct platform_device *pdev)
 	for (i = 0; i < iommu->num_clocks; ++i)
 		iommu->clocks[i].id = rk_iommu_clocks[i];
 
+	/*
+	 * iommu clocks should be present for all new devices and devicetrees
+	 * but there are older devicetrees without clocks out in the wild.
+	 * So clocks as optional for the time being.
+	 */
 	err = devm_clk_bulk_get(iommu->dev, iommu->num_clocks, iommu->clocks);
-	if (err)
+	if (err == -ENOENT)
+		iommu->num_clocks = 0;
+	else if (err)
 		return err;
 
 	err = clk_bulk_prepare(iommu->num_clocks, iommu->clocks);
-- 
2.16.2