Re: [Patch v15 4/5] dt-bindings: arm-smmu: Add bindings for qcom,smmu-v2

From: Vivek Gautam
Date: Fri Aug 31 2018 - 05:52:06 EST


Hi Rob,


On 8/30/2018 6:13 AM, Rob Herring wrote:
On Wed, Aug 29, 2018 at 6:23 AM Vivek Gautam
<vivek.gautam@xxxxxxxxxxxxxx> wrote:
On Wed, Aug 29, 2018 at 2:05 PM Vivek Gautam
<vivek.gautam@xxxxxxxxxxxxxx> wrote:
Hi Rob,


On 8/29/2018 2:04 AM, Rob Herring wrote:
On Mon, Aug 27, 2018 at 04:25:50PM +0530, Vivek Gautam wrote:
Add bindings doc for Qcom's smmu-v2 implementation.

Signed-off-by: Vivek Gautam <vivek.gautam@xxxxxxxxxxxxxx>
Reviewed-by: Tomasz Figa <tfiga@xxxxxxxxxxxx>
Tested-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
---

Changes since v14:
- This is a new patch added in v15 after noticing the new
checkpatch warning for separate dt-bindings doc.
- This patch also addresses comments given by Rob and Robin to add
a list of valid values of '<soc>' in "qcom,<soc>-smmu-v2"
compatible string.

.../devicetree/bindings/iommu/arm,smmu.txt | 47 ++++++++++++++++++++++
1 file changed, 47 insertions(+)

diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.txt b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
index 8a6ffce12af5..52198a539606 100644
--- a/Documentation/devicetree/bindings/iommu/arm,smmu.txt
+++ b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
@@ -17,10 +17,24 @@ conditions.
"arm,mmu-401"
"arm,mmu-500"
"cavium,smmu-v2"
+ "qcom,<soc>-smmu-v2", "qcom,smmu-v2"
The v2 in the compatible string is kind of redundant unless the SoC has
other SMMU types.
sdm845 has smmu-v2, and smmu-500 [1].

depending on the particular implementation and/or the
version of the architecture implemented.

+ A number of Qcom SoCs use qcom,smmu-v2 version of the IP.
+ "qcom,<soc>-smmu-v2" represents a soc specific compatible
+ string that should be present along with the "qcom,smmu-v2"
+ to facilitate SoC specific clocks/power connections and to
+ address specific bug fixes.
+ '<soc>' string in "qcom,<soc>-smmu-v2" should be one of the
+ following:
+ msm8996 - for msm8996 Qcom SoC.
+ sdm845 - for sdm845 Qcom Soc.
Rather than all this prose, it would be simpler to just add 2 lines with
the full compatibles rather than <soc>. The <soc> thing is not going to
work when/if we move bindings to json-schema also.
then we keep adding
"qcom,msm8996-smmu-v2", "qcom,smmu-v2"
"qcom,msm8998-smmu-v2", "qcom,smmu-v2"
"qcom,sdm845-smmu-v2", "qcom,smmu-v2",
and from [1]
"qcom,sdm845-smmu-500", "arm,mmu-500", etc.
for each SoCs?
How about following diff on top of this patch?

diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.txt
b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
index 52198a539606..5e6c04876533 100644
--- a/Documentation/devicetree/bindings/iommu/arm,smmu.txt
+++ b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
@@ -17,23 +17,18 @@ conditions.
"arm,mmu-401"
"arm,mmu-500"
"cavium,smmu-v2"
- "qcom,<soc>-smmu-v2", "qcom,smmu-v2"
+ "qcom,smmu-v2"

depending on the particular implementation and/or the
version of the architecture implemented.

- A number of Qcom SoCs use qcom,smmu-v2 version of the IP.
- "qcom,<soc>-smmu-v2" represents a soc specific compatible
- string that should be present along with the "qcom,smmu-v2"
- to facilitate SoC specific clocks/power connections and to
- address specific bug fixes.
- '<soc>' string in "qcom,<soc>-smmu-v2" should be one of the
- following:
- msm8996 - for msm8996 Qcom SoC.
- sdm845 - for sdm845 Qcom Soc.
-
- An example string would be -
- "qcom,msm8996-smmu-v2", "qcom,smmu-v2".
+ Qcom SoCs using qcom,smmu-v2 must have soc specific
+ compatible string attached to "qcom,smmu-v2" to take care
+ of SoC specific clocks/power connections and to address
+ specific bug fixes.
+ Precisely, it should be one of the following:
+ "qcom,msm8996-smmu-v2", "qcom,smmu-v2",
+ "qcom,sdm845-smmu-v2", "qcom,smmu-v2".
We don't need an explanation of why we need specific compatibles in
each binding document (though maybe we need a better explanation
somewhere). We just need to know what are valid values for compatibles
and this includes any combinations. Generally, this is just a list of
combinations.
[snip]

Fixed this in v16. Thanks.

Best regards
Vivek