Re: [PATCH 1/2] dt-bindings: iommu/rockchip: Make clock properties optional
Am Freitag, 13. April 2018, 23:02:26 CEST schrieb Rob Herring: > On Tue, Apr 10, 2018 at 01:26:41PM +0200, Heiko Stuebner wrote: > > Hi Robin, > > > > Am Dienstag, 10. April 2018, 13:18:48 CEST schrieb Robin Murphy: > > > On 10/04/18 10:26, Heiko Stuebner wrote: > > > > Rockchip IOMMUs are used without explicit clock handling for 4 years > > > > now, so we should keep compatibility with old devicetrees if possible. > > > > Therefore make iommu clocks optional. > > > > > > Do we need to touch the binding itself? Obviously the driver has to > > > treat clocks as optional in existing DTs (and I feel a bit dumb now for > > > managing to overlook that in review), but the binding effectively only > > > covers future DTs, and I'd assume we want to encourage the clocks to be > > > correctly specified there. > > I'd prefer the DT docs reflect what is correct for new/current dts > files. That's the only way the docs can validate the dts files. > > > I guess that depends on your definition of the timespan for backwards > > compatibility. I'm always starting out at indefinite till convinced > > otherwise ;-). Hence the clocks would need to stay optional for (nearly) > > forever. > > > > Also, having the binding claim them as required but the code handling > > them as optional just calls for someone to remove the optional handling :-D > > A comment in the code saying why missing clocks are allowed should > suffice. > > > Not sure if there is a established way of saying > > "we want this for all future devices, but allow it to be missing for old > > dts". > > We don't really... Ok, I'll drop the binding change and add a code comment then. Heiko ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH 1/2] dt-bindings: iommu/rockchip: Make clock properties optional
On Tue, Apr 10, 2018 at 01:26:41PM +0200, Heiko Stuebner wrote: > Hi Robin, > > Am Dienstag, 10. April 2018, 13:18:48 CEST schrieb Robin Murphy: > > On 10/04/18 10:26, Heiko Stuebner wrote: > > > Rockchip IOMMUs are used without explicit clock handling for 4 years > > > now, so we should keep compatibility with old devicetrees if possible. > > > Therefore make iommu clocks optional. > > > > Do we need to touch the binding itself? Obviously the driver has to > > treat clocks as optional in existing DTs (and I feel a bit dumb now for > > managing to overlook that in review), but the binding effectively only > > covers future DTs, and I'd assume we want to encourage the clocks to be > > correctly specified there. I'd prefer the DT docs reflect what is correct for new/current dts files. That's the only way the docs can validate the dts files. > I guess that depends on your definition of the timespan for backwards > compatibility. I'm always starting out at indefinite till convinced > otherwise ;-). Hence the clocks would need to stay optional for (nearly) > forever. > > Also, having the binding claim them as required but the code handling > them as optional just calls for someone to remove the optional handling :-D A comment in the code saying why missing clocks are allowed should suffice. > Not sure if there is a established way of saying > "we want this for all future devices, but allow it to be missing for old dts". We don't really... Rob ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH 1/2] dt-bindings: iommu/rockchip: Make clock properties optional
Hi Robin, Am Dienstag, 10. April 2018, 13:18:48 CEST schrieb Robin Murphy: > On 10/04/18 10:26, Heiko Stuebner wrote: > > Rockchip IOMMUs are used without explicit clock handling for 4 years > > now, so we should keep compatibility with old devicetrees if possible. > > Therefore make iommu clocks optional. > > Do we need to touch the binding itself? Obviously the driver has to > treat clocks as optional in existing DTs (and I feel a bit dumb now for > managing to overlook that in review), but the binding effectively only > covers future DTs, and I'd assume we want to encourage the clocks to be > correctly specified there. I guess that depends on your definition of the timespan for backwards compatibility. I'm always starting out at indefinite till convinced otherwise ;-). Hence the clocks would need to stay optional for (nearly) forever. Also, having the binding claim them as required but the code handling them as optional just calls for someone to remove the optional handling :-D Not sure if there is a established way of saying "we want this for all future devices, but allow it to be missing for old dts". Heiko ___ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
Re: [PATCH 1/2] dt-bindings: iommu/rockchip: Make clock properties optional
On 10/04/18 10:26, Heiko Stuebner wrote:
Rockchip IOMMUs are used without explicit clock handling for 4 years
now, so we should keep compatibility with old devicetrees if possible.
Therefore make iommu clocks optional.
Do we need to touch the binding itself? Obviously the driver has to
treat clocks as optional in existing DTs (and I feel a bit dumb now for
managing to overlook that in review), but the binding effectively only
covers future DTs, and I'd assume we want to encourage the clocks to be
correctly specified there.
Robin.
Fixes: 8fa9eb39c614 ("dt-bindings: iommu/rockchip: Add clock property")
Signed-off-by: Heiko Stuebner
---
Documentation/devicetree/bindings/iommu/rockchip,iommu.txt | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt
b/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt
index 6ecefea1c6f9..25bfad987513 100644
--- a/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt
+++ b/Documentation/devicetree/bindings/iommu/rockchip,iommu.txt
@@ -14,13 +14,13 @@ Required properties:
"single-master" device, and needs no additional
information
to associate with its master device. See:
Documentation/devicetree/bindings/iommu/iommu.txt
+
+Optional properties:
- clocks : A list of clocks required for the IOMMU to be accessible
by
the host CPU.
- clock-names : Should contain the following:
"iface" - Main peripheral bus clock (PCLK/HCL) (required)
"aclk" - AXI bus clock (required)
-
-Optional properties:
- rockchip,disable-mmu-reset : Don't use the mmu reset operation.
Some mmu instances may produce unexpected results
when the reset operation is used.
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