Re: [PATCH 01/11] dt-bindings: clock: Add RaspberryPi RP1 clock bindings

From: Andrea della Porta
Date: Thu Aug 22 2024 - 05:36:11 EST

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In reply to: Conor Dooley: "Re: [PATCH 01/11] dt-bindings: clock: Add RaspberryPi RP1 clock bindings"
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Hi Conor,

On 12:46 Wed 21 Aug , Conor Dooley wrote:
> On Tue, Aug 20, 2024 at 08:25:36PM +0200, Andrea della Porta wrote:
> > Hi Conor,
> >
> > On 17:19 Tue 20 Aug , Conor Dooley wrote:
> > > On Tue, Aug 20, 2024 at 04:36:03PM +0200, Andrea della Porta wrote:
> > > > Add device tree bindings for the clock generator found in RP1 multi
> > > > function device, and relative entries in MAINTAINERS file.
> > > >
> > > > Signed-off-by: Andrea della Porta <andrea.porta@xxxxxxxx>
> > > > ---
> > > > .../clock/raspberrypi,rp1-clocks.yaml | 87 +++++++++++++++++++
> > > > MAINTAINERS | 6 ++
> > > > include/dt-bindings/clock/rp1.h | 56 ++++++++++++
> > > > 3 files changed, 149 insertions(+)
> > > > create mode 100644 Documentation/devicetree/bindings/clock/raspberrypi,rp1-clocks.yaml
> > > > create mode 100644 include/dt-bindings/clock/rp1.h
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/clock/raspberrypi,rp1-clocks.yaml b/Documentation/devicetree/bindings/clock/raspberrypi,rp1-clocks.yaml
> > > > new file mode 100644
> > > > index 000000000000..b27db86d0572
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/clock/raspberrypi,rp1-clocks.yaml
> > > > @@ -0,0 +1,87 @@
> > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > > +%YAML 1.2
> > > > +---
> > > > +$id: http://devicetree.org/schemas/clock/raspberrypi,rp1-clocks.yaml#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +
> > > > +title: RaspberryPi RP1 clock generator
> > > > +
> > > > +maintainers:
> > > > + - Andrea della Porta <andrea.porta@xxxxxxxx>
> > > > +
> > > > +description: |
> > > > + The RP1 contains a clock generator designed as three PLLs (CORE, AUDIO,
> > > > + VIDEO), and each PLL output can be programmed though dividers to generate
> > > > + the clocks to drive the sub-peripherals embedded inside the chipset.
> > > > +
> > > > + Link to datasheet:
> > > > + https://datasheets.raspberrypi.com/rp1/rp1-peripherals.pdf
> > > > +
> > > > +properties:
> > > > + compatible:
> > > > + const: raspberrypi,rp1-clocks
> > > > +
> > > > + reg:
> > > > + maxItems: 1
> > > > +
> > > > + '#clock-cells':
> > > > + description:
> > > > + The index in the assigned-clocks is mapped to the output clock as per
> > > > + definitions in dt-bindings/clock/rp1.h.
> > > > + const: 1
> > > > +
> > > > + clocks:
> > > > + maxItems: 1
> > > > +
> > > > +required:
> > > > + - compatible
> > > > + - reg
> > > > + - '#clock-cells'
> > > > + - clocks
> > > > +
> > > > +additionalProperties: false
> > > > +
> > > > +examples:
> > > > + - |
> > > > + #include <dt-bindings/clock/rp1.h>
> > > > +
> > > > + rp1 {
> > > > + #address-cells = <2>;
> > > > + #size-cells = <2>;
> > > > +
> > > > + rp1_clocks: clocks@18000 {
> > >
> > > The unit address does not match the reg property. I'm surprised that
> > > dtc doesn't complain about that.
> >
> > Agreed. I'll update the address with the reg value in the next release
> >
> > >
> > > > + compatible = "raspberrypi,rp1-clocks";
> > > > + reg = <0xc0 0x40018000 0x0 0x10038>;
> > >
> > > This is a rather oddly specific size. It leads me to wonder if this
> > > region is inside some sort of syscon area?
> >
> > >From downstream source code and RP1 datasheet it seems that the last addressable
> > register is at 0xc040028014 while the range exposed through teh devicetree ends
> > up at 0xc040028038, so it seems more of a little safe margin. I wouldn't say it
> > is a syscon area since those register are quite specific for video clock
> > generation and not to be intended to be shared among different peripherals.
> > Anyway, the next register aperture is at 0xc040030000 so I would say we can
> > extend the clock mapped register like the following:
> >
> > reg = <0xc0 0x40018000 0x0 0x18000>;
> >
> > if you think it is more readable.
>
> I don't care

Ack.

> > > > + #clock-cells = <1>;
> > > > + clocks = <&clk_xosc>;
> > > > +
> > > > + assigned-clocks = <&rp1_clocks RP1_PLL_SYS_CORE>,
> >
> > > FWIW, I don't think any of these assigned clocks are helpful for the
> > > example. That said, why do you need to configure all of these assigned
> > > clocks via devicetree when this node is the provider of them?
> >
> > Not sure to understand what you mean here, the example is there just to
> > show how to compile the dt node, maybe you're referring to the fact that
> > the consumer should setup the clock freq?
>
> I suppose, yeah. I don't think a particular configuration is relevant
> for the example binding, but simultaneously don't get why you are
> assigning the rate for clocks used by audio devices or ethernet in the
> clock provider node.
>

Honestly I don't have a strong preference here, I can manage to do some tests
moving the clock rate settings inside the consumer nodes but I kinda like
the curernt idea of a centralized node where clocks are setup beforehand.
In RP1 the clock generator and peripherals such as ethernet are all on-board
and cannot be rewired in any other way so the devices are not standalone
consumer in their own right (such it would be an ethernet chip wired to an
external CPU). But of course this is debatable, on the other hand the current
approach of provider/consumer is of course very clean. I'm just wondering
wthether you think I should take action on this or we can leave it as it is.
Please see also below.

> > Consider that the rp1-clocks
> > is coupled to the peripherals contained in the same RP1 chip so there is
> > not much point in letting the peripherals set the clock to their leisure.
>
> How is that any different to the many other SoCs in the kernel?

In fact, it isn't. Please take a look at:

arch/arm/boot/dts/st/stm32mp15xx-dhcom-som.dtsi
arch/arm/boot/dts/ti/omap/omap44xx-clocks.dtsi
arch/arm/boot/dts/ti/omap/dra7xx-clocks.dtsi
arch/arm/boot/dts/nxp/imx/imx7d-zii-rpu2.dts

and probably many others... they use the same approach, so I assumed it is at
least reasonable to assign the clock rate this way.

Many thanks,
Andrea

>
> > > > + <&rp1_clocks RP1_PLL_AUDIO_CORE>,
> > > > + /* RP1_PLL_VIDEO_CORE and dividers are now managed by VEC,DPI drivers */
> > >
> > > Comments like this also do not seem relevant to the binding.
> >
> > Agreed, will drop in the next release.
> >
> > >
> > >
> > > Cheers,
> > > Conor.
> > >
> >
> > Many thanks,
> > Andrea
> >
> > >
> > > > + <&rp1_clocks RP1_PLL_SYS>,
> > > > + <&rp1_clocks RP1_PLL_SYS_SEC>,
> > > > + <&rp1_clocks RP1_PLL_AUDIO>,
> > > > + <&rp1_clocks RP1_PLL_AUDIO_SEC>,
> > > > + <&rp1_clocks RP1_CLK_SYS>,
> > > > + <&rp1_clocks RP1_PLL_SYS_PRI_PH>,
> > > > + /* RP1_CLK_SLOW_SYS is used for the frequency counter (FC0) */
> > > > + <&rp1_clocks RP1_CLK_SLOW_SYS>,
> > > > + <&rp1_clocks RP1_CLK_SDIO_TIMER>,
> > > > + <&rp1_clocks RP1_CLK_SDIO_ALT_SRC>,
> > > > + <&rp1_clocks RP1_CLK_ETH_TSU>;
> > > > +
> > > > + assigned-clock-rates = <1000000000>, // RP1_PLL_SYS_CORE
> > > > + <1536000000>, // RP1_PLL_AUDIO_CORE
> > > > + <200000000>, // RP1_PLL_SYS
> > > > + <125000000>, // RP1_PLL_SYS_SEC
> > > > + <61440000>, // RP1_PLL_AUDIO
> > > > + <192000000>, // RP1_PLL_AUDIO_SEC
> > > > + <200000000>, // RP1_CLK_SYS
> > > > + <100000000>, // RP1_PLL_SYS_PRI_PH
> > > > + /* Must match the XOSC frequency */
> > > > + <50000000>, // RP1_CLK_SLOW_SYS
> > > > + <1000000>, // RP1_CLK_SDIO_TIMER
> > > > + <200000000>, // RP1_CLK_SDIO_ALT_SRC
> > > > + <50000000>; // RP1_CLK_ETH_TSU
> > > > + };
> > > > + };
> > > > diff --git a/MAINTAINERS b/MAINTAINERS
> > > > index 42decde38320..6e7db9bce278 100644
> > > > --- a/MAINTAINERS
> > > > +++ b/MAINTAINERS
> > > > @@ -19116,6 +19116,12 @@ F: Documentation/devicetree/bindings/media/raspberrypi,pispbe.yaml
> > > > F: drivers/media/platform/raspberrypi/pisp_be/
> > > > F: include/uapi/linux/media/raspberrypi/
> > > >
> > > > +RASPBERRY PI RP1 PCI DRIVER
> > > > +M: Andrea della Porta <andrea.porta@xxxxxxxx>
> > > > +S: Maintained
> > > > +F: Documentation/devicetree/bindings/clock/raspberrypi,rp1-clocks.yaml
> > > > +F: include/dt-bindings/clock/rp1.h
> > > > +
> > > > RC-CORE / LIRC FRAMEWORK
> > > > M: Sean Young <sean@xxxxxxxx>
> > > > L: linux-media@xxxxxxxxxxxxxxx
> > > > diff --git a/include/dt-bindings/clock/rp1.h b/include/dt-bindings/clock/rp1.h
> > > > new file mode 100644
> > > > index 000000000000..1ed67b8a5229
> > > > --- /dev/null
> > > > +++ b/include/dt-bindings/clock/rp1.h
> > > > @@ -0,0 +1,56 @@
> > > > +/* SPDX-License-Identifier: GPL-2.0 OR MIT */
> > > > +/*
> > > > + * Copyright (C) 2021 Raspberry Pi Ltd.
> > > > + */
> > > > +
> > > > +#define RP1_PLL_SYS_CORE 0
> > > > +#define RP1_PLL_AUDIO_CORE 1
> > > > +#define RP1_PLL_VIDEO_CORE 2
> > > > +
> > > > +#define RP1_PLL_SYS 3
> > > > +#define RP1_PLL_AUDIO 4
> > > > +#define RP1_PLL_VIDEO 5
> > > > +
> > > > +#define RP1_PLL_SYS_PRI_PH 6
> > > > +#define RP1_PLL_SYS_SEC_PH 7
> > > > +#define RP1_PLL_AUDIO_PRI_PH 8
> > > > +
> > > > +#define RP1_PLL_SYS_SEC 9
> > > > +#define RP1_PLL_AUDIO_SEC 10
> > > > +#define RP1_PLL_VIDEO_SEC 11
> > > > +
> > > > +#define RP1_CLK_SYS 12
> > > > +#define RP1_CLK_SLOW_SYS 13
> > > > +#define RP1_CLK_DMA 14
> > > > +#define RP1_CLK_UART 15
> > > > +#define RP1_CLK_ETH 16
> > > > +#define RP1_CLK_PWM0 17
> > > > +#define RP1_CLK_PWM1 18
> > > > +#define RP1_CLK_AUDIO_IN 19
> > > > +#define RP1_CLK_AUDIO_OUT 20
> > > > +#define RP1_CLK_I2S 21
> > > > +#define RP1_CLK_MIPI0_CFG 22
> > > > +#define RP1_CLK_MIPI1_CFG 23
> > > > +#define RP1_CLK_PCIE_AUX 24
> > > > +#define RP1_CLK_USBH0_MICROFRAME 25
> > > > +#define RP1_CLK_USBH1_MICROFRAME 26
> > > > +#define RP1_CLK_USBH0_SUSPEND 27
> > > > +#define RP1_CLK_USBH1_SUSPEND 28
> > > > +#define RP1_CLK_ETH_TSU 29
> > > > +#define RP1_CLK_ADC 30
> > > > +#define RP1_CLK_SDIO_TIMER 31
> > > > +#define RP1_CLK_SDIO_ALT_SRC 32
> > > > +#define RP1_CLK_GP0 33
> > > > +#define RP1_CLK_GP1 34
> > > > +#define RP1_CLK_GP2 35
> > > > +#define RP1_CLK_GP3 36
> > > > +#define RP1_CLK_GP4 37
> > > > +#define RP1_CLK_GP5 38
> > > > +#define RP1_CLK_VEC 39
> > > > +#define RP1_CLK_DPI 40
> > > > +#define RP1_CLK_MIPI0_DPI 41
> > > > +#define RP1_CLK_MIPI1_DPI 42
> > > > +
> > > > +/* Extra PLL output channels - RP1B0 only */
> > > > +#define RP1_PLL_VIDEO_PRI_PH 43
> > > > +#define RP1_PLL_AUDIO_TERN 44
> > > > --
> > > > 2.35.3
> > > >
> >
> >

Next message: David Lin: "RE: [EXT] [PATCH 10/31] wifi: mwifiex: fix indention"
Previous message: Charles Han: "[PATCH] drm/panel: fix null pointer dereference in hx83102_get_modes"
In reply to: Conor Dooley: "Re: [PATCH 01/11] dt-bindings: clock: Add RaspberryPi RP1 clock bindings"
Next in thread: Krzysztof Kozlowski: "Re: [PATCH 01/11] dt-bindings: clock: Add RaspberryPi RP1 clock bindings"
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