linux-kernel - Re: [PATCH RFC 1/2] dt-bindings: interconnect: qcom: add msm8974 bindings

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Message-ID: <20190904190357.GI574@tuxbook-pro>
Date:   Wed, 4 Sep 2019 12:03:57 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Brian Masney <masneyb@...tation.org>
Cc:     georgi.djakov@...aro.org, linux-arm-msm@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 1/2] dt-bindings: interconnect: qcom: add msm8974
 bindings

On Wed 04 Sep 03:20 PDT 2019, Brian Masney wrote:

> On Tue, Sep 03, 2019 at 10:01:03PM -0700, Bjorn Andersson wrote:
> > On Mon 02 Sep 14:19 PDT 2019, Brian Masney wrote:
> > > +      mmssnoc: interconnect@...78000 {
> > > +              reg = <0xfc478000 0x4000>;
> > > +              compatible = "qcom,msm8974-mmssnoc";
> > > +              #interconnect-cells = <1>;
> > > +              clock-names = "bus", "bus_a";
> > > +              clocks = <&rpmcc RPM_SMD_MMSSNOC_AHB_CLK>,
> > > +                       <&rpmcc RPM_SMD_MMSSNOC_AHB_A_CLK>;
> > 
> > Isn't MMSS_S0_AXI_CLK the bus clock of the mmssnoc (which somehow seems
> > to depend on mmssnoc_ahb_clk)?
> 
> I'll give that a try. Do you know which clock I should use for bus_a
> here? On the mmcc, I see the following mmss clocks available:
> 
> MMSS_AHB_CLK_SRC
> MMSS_AXI_CLK_SRC
> MMSS_RBCPR_CLK_SRC
> MMSS_MISC_AHB_CLK
> MMSS_MMSSNOC_AHB_CLK
> MMSS_MMSSNOC_BTO_AHB_CLK
> MMSS_MMSSNOC_AXI_CLK
> MMSS_S0_AXI_CLK
> 
> I'm also unsure of what's going on at the hardware level that the second
> clock (bus_a) is needed.
> 

In msm-3.4 clock-8974.c both bus and bus_a is defined as
mmss_s0_axi_clk. But iirc I also needed mmssnoc_axi_clk to get DSI
working on my devices, which is listed as .depends of the s0_axi clock.

So that probably needs some more investigation...But easiest would
probably be to just have the mmss_noc use them both listed as bus
clocks?

Regards,
Bjorn

> > > +      mdss: mdss@...00000 {
> > 
> > I think you can omit the client, as this adheres to the standard binding
> > for interconnect clients. And you don't need to have an example that
> > covers all compatibles either...
> 
> OK, I'll drop some of these.
> 
> > > diff --git a/include/dt-bindings/interconnect/qcom,msm8974.h b/include/dt-bindings/interconnect/qcom,msm8974.h
> > > new file mode 100644
> > > index 000000000000..58acf7196410
> > > --- /dev/null
> > > +++ b/include/dt-bindings/interconnect/qcom,msm8974.h
> > > @@ -0,0 +1,146 @@
> > > +/* SPDX-License-Identifier: GPL-2.0 */
> > 
> > Would you mind dual licensing this part as well?
> 
> Sure, that was an oversight on my part.
> 
> > Apart from that, I think this binding looks good.
> 
> Thanks,
> 
> Brian