Re: [PATCH 1/4] dt-bindings: reset: Add PDC reset binding for SDM845 SoCs

[Sibi S]

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@xxxxxxxxxxxxxx>
> > ---
> >   .../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@b2e0000 {
>
> 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.

> > +	compatible = "qcom,sdm845-pdc-global";
> > +	reg = <0xb2e0000 0x20000>;
>
> This looks like this is the register space of the complete PDC, not just
> the reset register?

The entire register space was chosen because it is only used for its
reset lines (had a good look at the downstream kernel and had a 
conversation with Lina) and to ensure break backward compatibility for
the for the dt entry if the reg-space was used for other purposes in
the future.

> > +	#reset-cells = <1>;
> > +};
> > +
> > +PDC reset clients
> > +======================================
> > +
> > +Device nodes that need access to reset lines should
> > +specify them as a reset phandle in their corresponding node as
> > +specified in reset.txt.
> > +
> > +For list of all valid reset indicies see
> > +<dt-bindings/reset/qcom,sdm845-pdc.h>
> > +
> > +Example:
> > +
> > +modem-pil@4080000 {
> > +	...
> > +
> > +	resets = <&pdc_reset PDC_MODEM_SYNC_RESET>;
> > +	reset-names = "pdc_restart";
> > +
> > +	...
> > +};
> > diff --git a/include/dt-bindings/reset/qcom,sdm845-pdc.h b/include/dt-bindings/reset/qcom,sdm845-pdc.h
> > new file mode 100644
> > index 000000000000..53c37f9c319a
> > --- /dev/null
> > +++ b/include/dt-bindings/reset/qcom,sdm845-pdc.h
> > @@ -0,0 +1,20 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (C) 2018 The Linux Foundation. All rights reserved.
> > + */
> > +
> > +#ifndef _DT_BINDINGS_RESET_PDC_SDM_845_H
> > +#define _DT_BINDINGS_RESET_PDC_SDM_845_H
> > +
> > +#define PDC_APPS_SYNC_RESET	0
> > +#define PDC_SP_SYNC_RESET	1
> > +#define PDC_AUDIO_SYNC_RESET	2
> > +#define PDC_SENSORS_SYNC_RESET	3
> > +#define PDC_AOP_SYNC_RESET	4
> > +#define PDC_DEBUG_SYNC_RESET	5
> > +#define PDC_GPU_SYNC_RESET	6
> > +#define PDC_DISPLAY_SYNC_RESET	7
> > +#define PDC_COMPUTE_SYNC_RESET	8
> > +#define PDC_MODEM_SYNC_RESET	9
> > +
> > +#endif
>
> regards
> Philipp

--
Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc, is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project