Re: [PATCH v2 1/2] dt-bindings: spi: Qualcomm Quad SPI(QSPI) documentation
From: Doug Anderson
Date: Tue Sep 25 2018 - 12:02:34 EST
Hi,
On Mon, Sep 24, 2018 at 11:23 AM Trent Piepho <tpiepho@xxxxxxxxxx> wrote:
>
> On Mon, 2018-09-24 at 10:13 -0700, Doug Anderson wrote:
> > IIUC previous suggestions about just naming it based on the first SoC
> > was due to the difficulty of coming up with a good generic name to
> > give something. For instance you definitely wouldn't want to name it
> > "qcom-qspi-sdm8xx" because you have no idea what future SoCs will be
> > numbered.
>
> And the hypothetical sdm899 might use a non-compatible device that uses
> a different driver, and that really makes "qcom-qspi-sdm8xx" look dumb.
>
> >
> > In the case here calling it "qcom,qspi-v1" is better than that and if
> > Rob gives the thumbs up then I won't object to it. In general though
> > looking at other device tree bindings this doesn't seem like a thing
> > commonly done. Perhaps if we decide it's useful here we should start
> > suggesting it everywhere...
>
> It would help if the programming model or IP core name or whatever this
> is using was mentioned in the public reference manual for the SoC.
> Then is a lot more clear that a number of different SoCs all have the
> same quad spi controller inside them.
>
> Usually it's not like that. The RMs just say, "it's got a SPI master
> with these registers." What SoCs use the same IP module, which
> different? When did they make a new version? The silicon vendors
> don't tell you this. So any name we make up for the IP module likely
> doesn't match reality.
Note that Rob did recently give a positive review to a similar binding. See:
https://lore.kernel.org/patchwork/patch/979432/
Specifically the text from that binding was:
+ Qcom SoCs must contain, as below, SoC-specific compatibles
+ along with "qcom,smmu-v2":
+ "qcom,msm8996-smmu-v2", "qcom,smmu-v2",
+ "qcom,sdm845-smmu-v2", "qcom,smmu-v2".
Given Rob's positive review there, it seems like it would be fine to do:
"qcom,sdm845-qspi", "qcom,qspi-v1".
NOTE: In our case we don't need the "-v1" in SoC-specific case since
there's only one Quad SPI driver there. As I understand it the reason
we needed the -v2 in the SoC-specific case for the SMMU was that there
are two totally different SMMUs in SDM845. You can see history in the
v15 patch <https://lore.kernel.org/patchwork/patch/977888/>
-Doug