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

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Date:   Wed, 29 Aug 2018 14:05:10 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Rob Herring <robh@...nel.org>
Cc:     joro@...tes.org, robin.murphy@....com, will.deacon@....com,
        iommu@...ts.linux-foundation.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, freedreno@...ts.freedesktop.org,
        alex.williamson@...hat.com, mark.rutland@....com,
        rjw@...ysocki.net, robdclark@...il.com, andy.gross@...aro.org,
        linux-pm@...r.kernel.org, sboyd@...nel.org, tfiga@...omium.org,
        jcrouse@...eaurora.org, sricharan@...eaurora.org,
        m.szyprowski@...sung.com, architt@...eaurora.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [Patch v15 4/5] dt-bindings: arm-smmu: Add bindings for
 qcom,smmu-v2

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@...eaurora.org>
>> Reviewed-by: Tomasz Figa <tfiga@...omium.org>
>> Tested-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>> ---
>>
>> 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?

>
>> +
>> +                  An example string would be -
>> +                  "qcom,msm8996-smmu-v2", "qcom,smmu-v2".
>> +
>>   - reg           : Base address and size of the SMMU.
>>   
>>   - #global-interrupts : The number of global interrupts exposed by the
>> @@ -71,6 +85,22 @@ conditions.
>>                     or using stream matching with #iommu-cells = <2>, and
>>                     may be ignored if present in such cases.
>>   
>> +- clock-names:    List of the names of clocks input to the device. The
>> +                  required list depends on particular implementation and
>> +                  is as follows:
>> +                  - for "qcom,smmu-v2":
>> +                    - "bus": clock required for downstream bus access and
>> +                             for the smmu ptw,
>> +                    - "iface": clock required to access smmu's registers
>> +                               through the TCU's programming interface.
>> +                  - unspecified for other implementations.
>> +
>> +- clocks:         Specifiers for all clocks listed in the clock-names property,
>> +                  as per generic clock bindings.
>> +
>> +- power-domains:  Specifiers for power domains required to be powered on for
>> +                  the SMMU to operate, as per generic power domain bindings.
>> +
>>   ** Deprecated properties:
>>   
>>   - mmu-masters (deprecated in favour of the generic "iommus" binding) :
>> @@ -137,3 +167,20 @@ conditions.
>>                   iommu-map = <0 &smmu3 0 0x400>;
>>                   ...
>>           };
>> +
>> +	/* Qcom's arm,smmu-v2 implementation */
>> +	smmu4: iommu {
> Needs a unit-address.

I went in symmetry with another example in this file for 'smmu1'. I will 
add the address here.
And if you would like, I can squash a change for 'smmu1' too in this 
patch, although that will be trivial.

[1] https://patchwork.kernel.org/patch/10565291/

Best regards
Vivek

[snip]