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Date:   Wed, 8 Aug 2018 15:37:24 -0600
From:   Jordan Crouse <jcrouse@...eaurora.org>
To:     Sibi Sankar <sibis@...eaurora.org>
Cc:     Rob Herring <robh@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        bjorn.andersson@...aro.org, linux-remoteproc@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        ohad@...ery.com, mark.rutland@....com, sricharan@...eaurora.org,
        akdwived@...eaurora.org, linux-arm-msm@...r.kernel.org,
        tsoni@...eaurora.org, ilina@...eaurora.org
Subject: Re: [PATCH 1/4] dt-bindings: reset: Add PDC reset binding for SDM845
 SoCs

On Wed, Aug 08, 2018 at 09:14:05PM +0530, Sibi Sankar wrote:
> Hi Rob,
> Thanks for the review
> 
> On 08/07/2018 11:46 PM, Rob Herring wrote:
> >On Tue, Jul 31, 2018 at 06:27:24PM +0530, Sibi S wrote:
> >>Hi Philipp,
> >>Thanks for the review!
> >>
> >>On 07/31/2018 02:12 PM, Philipp Zabel wrote:
> >>>Hi Sibi,
> >>>
> >>>On Fri, 2018-07-27 at 20:58 +0530, Sibi Sankar wrote:
> >>>>Add SDM845 PDC (Power Domain Controller) reset controller binding
> >>>>
> >>>>Signed-off-by: Sibi Sankar <sibis@...eaurora.org>
> >>>>---
> >>>>   .../bindings/reset/qcom,pdc-reset.txt         | 52 +++++++++++++++++++
> >>>>   include/dt-bindings/reset/qcom,sdm845-pdc.h   | 20 +++++++
> >>>>   2 files changed, 72 insertions(+)
> >>>>   create mode 100644 Documentation/devicetree/bindings/reset/qcom,pdc-reset.txt
> >>>>   create mode 100644 include/dt-bindings/reset/qcom,sdm845-pdc.h
> >>>>
> >>>>diff --git a/Documentation/devicetree/bindings/reset/qcom,pdc-reset.txt b/Documentation/devicetree/bindings/reset/qcom,pdc-reset.txt
> >>>>new file mode 100644
> >>>>index 000000000000..85e159962e08
> >>>>--- /dev/null
> >>>>+++ b/Documentation/devicetree/bindings/reset/qcom,pdc-reset.txt
> >>>>@@ -0,0 +1,52 @@
> >>>>+PDC Reset Controller
> >>>>+======================================
> >>>>+
> >>>>+This binding describes a reset-controller found on PDC-Global(Power Domain
> >>>>+Controller) block for Qualcomm Technologies Inc SDM845 SoCs.
> >>>>+
> >>>>+Required properties:
> >>>>+- compatible:
> >>>>+	Usage: required
> >>>>+	Value type: <string>
> >>>>+	Definition: must be:
> >>>>+		    "qcom,sdm845-pdc-global"
> >>>>+
> >>>>+- reg:
> >>>>+	Usage: required
> >>>>+	Value type: <prop-encoded-array>
> >>>>+	Definition: must specify the base address and size of the register
> >>>>+	            space.
> >>>>+
> >>>>+- #reset-cells:
> >>>>+	Usage: required
> >>>>+	Value type: <uint>
> >>>>+	Definition: must be 1; cell entry represents the reset index.
> >>>>+
> >>>>+Example:
> >>>>+
> >>>>+pdc_reset: reset-controller@...0000 {
> >>>
> >>>Is this really just a reset controller?
> >>>
> >>>The name makes it sound like a driver binding to this should also
> >>>provide pm_genpd and the binding should probably call this a power-
> >>>controller: Documentation/devicetree/bindings/power/power_domain.txt.
> >>>
> >>
> >>The PDC-global reg space which is a part of PDC-wrapper reg space seems
> >>to be only used for the reset lines.
> >>
> >>Couple of other drivers use other parts of the PDC-wrapper reg space:
> >>https://patchwork.kernel.org/patch/10223701/ (PDC-Interrupt controller)
> >>https://patchwork.kernel.org/patch/10255767/ (GMU-PDC incorrectly tries
> >>to occupy the entire pdc-wrapper reg space)
> >>
> >>since it couldn't be logically mapped into pdc-interrupt driver, it had
> >>to be included as a separate reset driver.
> >
> >You can't have overlapping regions in DT (well, you can because we have
> >to work-around existing DTs that do, but you shouldn't).
> >
> >A single node can be multiple providers such as interrupt controller and
> >reset controller. It's an OS problem to split that into multiple
> >drivers.
> 
> There will be no overlaps. Jordan will be changing the dt binding of
> gmu_pdc so that there is no overlap I guess. What I meant to say is that
> pdc-global is a separate reg-space and currently has no other
> functionality other than exposing the reset lines.

Correct - the updated GPU DT will be:

  reg = <0x506a000 0x30000>,
     <0xb280000 0x10000>,
     <0xb480000, 0x10000>;
  reg-names = "gmu", "gmu_pdc", "gmu_pdc_seq";

Jordan

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