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From: Matthias Kaehlcke <mka@chromium.org>
To: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Sibi Sankar <sibis@codeaurora.org>,
	sboyd@kernel.org, robh+dt@kernel.org, viresh.kumar@linaro.org,
	agross@kernel.org, rjw@rjwysocki.net,
	linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	dianders@chromium.org, tdas@codeaurora.org
Subject: Re: [PATCH 4/4] arm64: dts: qcom: sm8350: Fixup the cpufreq node
Date: Wed, 4 Aug 2021 16:58:38 -0700	[thread overview]
Message-ID: <YQsprr4rLVPwVfqR@google.com> (raw)
In-Reply-To: <YQsbuN1xyAlCYRqK@builder.lan>

On Wed, Aug 04, 2021 at 05:59:04PM -0500, Bjorn Andersson wrote:
> On Thu 29 Jul 13:04 CDT 2021, Sibi Sankar wrote:
> 
> > Fixup the register regions used by the cpufreq node on SM8350 SoC to
> > support per core L3 DCVS.
> > 
> 
> That sounds good, but why are you dropping the platform-specific
> compatible?
> 

I also stared at this and the patch that changes the code for a while.

My understanding is that removing the platform-specific compatible is part
of not breaking 'old' DTBs. Old DTBs for SM8350 contain the larger register
regions and must be paired with 'epss_sm8250_soc_data' (driver code) which
has the 'old' 'reg_perf_state' offset. New SM8350 DTs only have the
'qcom,cpufreq-epss' compatible, which pairs their smaller register regions
with 'epss_soc_data' with the new 'reg_perf_state' offset.

It is super-confusing that the platform-specific compatible string is
missing. The binding should probably mention that the two
platform-specific compatible strings are for backwards compatibility
only and should not be added to new or existing DT files that don't
have them already. Maybe a 'qcom,sm8350-cpufreq-epss-v2' or similar
should be added to avoid/reduce possible confusion and have to option
to add SM8350 specific code later.

  reply	other threads:[~2021-08-04 23:58 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-29 18:04 [PATCH 0/4] Fixup register offsets to support per core L3 DCVS Sibi Sankar
2021-07-29 18:04 ` [PATCH 1/4] dt-bindings: cpufreq: cpufreq-qcom-hw: Add compatible for SM8250/8350 Sibi Sankar
2021-08-03 19:23   ` Rob Herring
2021-08-04 18:56   ` Stephen Boyd
2021-07-29 18:04 ` [PATCH 2/4] cpufreq: qcom: Re-arrange register offsets to support per core L3 DCVS Sibi Sankar
2021-08-04 19:01   ` Stephen Boyd
2021-08-05 17:47     ` Sibi Sankar
2021-08-05 18:25       ` Stephen Boyd
2021-08-06  6:42         ` Sibi Sankar
2021-08-04 23:11   ` Bjorn Andersson
2021-08-04 23:20     ` Bjorn Andersson
2021-07-29 18:04 ` [PATCH 3/4] arm64: dts: qcom: sc7280: Fixup the cpufreq node Sibi Sankar
2021-08-04 18:57   ` Stephen Boyd
2021-08-31 15:30   ` Matthias Kaehlcke
2021-08-31 17:04     ` Bjorn Andersson
2021-09-06  3:20       ` Sibi Sankar
2021-09-07 19:14         ` Doug Anderson
2021-07-29 18:04 ` [PATCH 4/4] arm64: dts: qcom: sm8350: " Sibi Sankar
2021-08-04 22:59   ` Bjorn Andersson
2021-08-04 23:58     ` Matthias Kaehlcke [this message]
2021-08-30  6:47       ` Sibi Sankar

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