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From: "Pali Rohár" <pali@kernel.org>
To: Stephen Boyd <sboyd@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Michael Turquette <mturquette@baylibre.com>,
	Rob Herring <robh+dt@kernel.org>, Andrew Lunn <andrew@lunn.ch>,
	Gregory Clement <gregory.clement@bootlin.com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>,
	Vladimir Vid <vladimir.vid@sartura.hr>,
	kabel@kernel.org, linux-clk@vger.kernel.org,
	linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock
Date: Thu, 12 Aug 2021 22:08:04 +0200	[thread overview]
Message-ID: <20210812200804.i4kbcs6ut27mapd3@pali> (raw)
In-Reply-To: <162879679919.19113.10297499909721773583@swboyd.mtv.corp.google.com>

On Thursday 12 August 2021 12:33:19 Stephen Boyd wrote:
> Quoting Pali (2021-08-06 01:28:18)
> > On Thursday 05 August 2021 17:30:19 Stephen Boyd wrote:
> > > > diff --git a/Documentation/devicetree/bindings/clock/armada3700-uart-clock.yaml b/Documentation/devicetree/bindings/clock/armada3700-uart-clock.yaml
> > > > new file mode 100644
> > > > index 000000000000..5ef04f3affda
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/clock/armada3700-uart-clock.yaml
> > > > @@ -0,0 +1,49 @@
> > > > +# SPDX-License-Identifier: GPL-2.0
> > > > +%YAML 1.2
> > > > +---
> > > > +$id: http://devicetree.org/schemas/clock/marvell,armada-3700-uart-clock#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +title: Marvell Armada 3720 UART clocks
> > > 
> > > Please add a newline here
> > > 
> > > > +properties:
> > > > +  compatible:
> > > > +    const: marvell,armada-3700-uart-clock
> > > 
> > > Please add a newline here
> > > 
> > > > +  reg:
> > > > +    items:
> > > > +      - description: UART Clock Control Register
> > > > +      - description: UART 2 Baud Rate Divisor Register
> > > 
> > > Please add a newline here
> > > 
> > > > +  clocks:
> > > > +    description: |
> > > > +      List of parent clocks suitable for UART from following set:
> > > > +        "TBG-A-P", "TBG-B-P", "TBG-A-S", "TBG-B-S", "xtal"
> > > > +      UART clock can use one from this set and when more are provided
> > > > +      then kernel would choose and configure the most suitable one.
> > > > +      It is suggest to specify at least one TBG clock to achieve
> > > > +      baudrates above 230400 and also to specify clock which bootloader
> > > > +      used for UART (most probably xtal) for smooth boot log on UART.
> > > 
> > > Please use items and const like clock-names for the clocks property.
> > 
> > It is already there, see below.
> > 
> > > The description makes me feel like the DT is configuring the choices
> > > available.
> > 
> > See description. It is kernel (driver) who is choosing one clock from
> > the set and then configure it a UART clock.
> 
> Can that be done with assigned-clock-parents?

I'm not sure if it is possible. Frequencies of "TBG-A-P", "TBG-B-P",
"TBG-A-S" and "TBG-B-S" clocks are set by firmware and frequency of
"xtal" by strapping pin. So they are not static constants. And also
kernel cannot change frequency of these clocks.

Driver reads frequencies of these clocks and choose the one which is the
most suitable for UART at runtime.

> > > Ideally, the clocks and clock-names properties are fixed in
> > > length and never change unless the compatible changes.
> > > 
> > > Please add a newline here
> > > 
> > > > +  clock-names:
> > > > +    items:
> > > > +      - const: TBG-A-P
> > > > +      - const: TBG-B-P
> > > > +      - const: TBG-A-S
> > > > +      - const: TBG-B-S
> > > > +      - const: xtal
> > > > +    minItems: 1
> > > > +    maxItems: 5
> > > 
> > > Please add a newline here
> > > 
> > > > +  '#clock-cells':
> > > > +    const: 1
> > > 
> > > Please add a newline here
> > > 
> > > > +required:
> > > > +  - compatible
> > > > +  - reg
> > > > +  - clocks
> > > > +  - clock-names
> > > > +  - '#clock-cells'
> > > 
> > > Please add a newline here
> > > 
> > > > +additionalProperties: false
> > > 
> > > Please add a newline here
> > > 
> > > > +examples:
> > > > +  - |
> > > > +    uartclk: uartclk@12000 {
> > > > +      compatible = "marvell,armada-3700-uart-clock";
> > > > +      reg = <0x12010 0x4>, <0x12210 0x4>;
> 
> The reg property looks like this is poking a mux that is part of a
> larger device. What device is this actually part of? The uart hardware?

Yes, UART hardware.

> > > > +      clocks = <&tbg 0>, <&tbg 1>, <&tbg 2>, <&tbg 3>, <&xtalclk>;
> > > > +      clock-names = "TBG-A-P", "TBG-B-P", "TBG-A-S", "TBG-B-S", "xtal";

  reply	other threads:[~2021-08-12 20:08 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-24 22:48 [PATCH 00/10] serial: mvebu-uart: Fixes and new support for higher baudrates Pali Rohár
2021-06-24 22:49 ` [PATCH 01/10] serial: mvebu-uart: fix calculation of clock divisor Pali Rohár
2021-06-24 22:49 ` [PATCH 02/10] serial: mvebu-uart: do not allow changing baudrate when uartclk is not available Pali Rohár
2021-06-24 22:49 ` [PATCH 03/10] serial: mvebu-uart: correctly calculate minimal possible baudrate Pali Rohár
2021-06-24 22:49 ` [PATCH 04/10] dt-bindings: mvebu-uart: fix documentation Pali Rohár
2021-06-24 22:49 ` [PATCH 05/10] arm64: dts: marvell: armada-37xx: Fix reg for standard variant of UART Pali Rohár
2021-06-24 22:49 ` [PATCH 06/10] serial: mvebu-uart: remove unused member nb from struct mvebu_uart Pali Rohár
2021-06-24 22:49 ` [PATCH 07/10] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-06-24 22:49 ` [PATCH 08/10] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-06-24 22:49 ` [PATCH 09/10] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-06-24 22:49 ` [PATCH 10/10] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-06-25 14:36 ` [PATCH v2 00/11] serial: mvebu-uart: Fixes and new support for higher baudrates Pali Rohár
2021-06-25 14:36   ` [PATCH v2 01/11] serial: mvebu-uart: fix calculation of clock divisor Pali Rohár
2021-06-25 14:36   ` [PATCH v2 02/11] serial: mvebu-uart: do not allow changing baudrate when uartclk is not available Pali Rohár
2021-06-25 14:36   ` [PATCH v2 03/11] serial: mvebu-uart: correctly calculate minimal possible baudrate Pali Rohár
2021-06-25 14:36   ` [PATCH v2 04/11] dt-bindings: mvebu-uart: fix documentation Pali Rohár
2021-06-25 14:36   ` [PATCH v2 05/11] arm64: dts: marvell: armada-37xx: Fix reg for standard variant of UART Pali Rohár
2021-06-25 14:36   ` [PATCH v2 06/11] serial: mvebu-uart: remove unused member nb from struct mvebu_uart Pali Rohár
2021-06-25 14:36   ` [PATCH v2 07/11] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár
2021-06-25 15:22     ` Geert Uytterhoeven
2021-06-25 15:38       ` Pali Rohár
2021-06-25 15:50         ` Willy Tarreau
2021-06-25 17:39           ` Geert Uytterhoeven
2021-06-25 17:44             ` Pali Rohár
2021-06-25 18:11               ` Geert Uytterhoeven
2021-07-19 12:45         ` Andy Shevchenko
2021-06-25 14:36   ` [PATCH v2 08/11] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-06-25 14:36   ` [PATCH v2 09/11] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-06-25 14:36   ` [PATCH v2 10/11] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-06-25 14:36   ` [PATCH v2 11/11] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-07-17 12:38 ` [PATCH v3 0/5] serial: mvebu-uart: Support for higher baudrates Pali Rohár
2021-07-17 12:38   ` [PATCH v3 1/5] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár
2021-07-19 12:47     ` Andy Shevchenko
2021-07-22 21:57       ` Pali Rohár
2021-07-24 11:38         ` David Laight
2021-07-17 12:38   ` [PATCH v3 2/5] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-07-17 17:26     ` Andrew Lunn
2021-07-17 18:05       ` Pali Rohár
2021-07-24  9:48         ` Pali Rohár
2021-07-24 16:33           ` Andrew Lunn
2021-07-25 12:14             ` Pali Rohár
2021-07-17 12:38   ` [PATCH v3 3/5] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-07-17 17:30     ` [PATCH v3 3/5] dt-bindings: mvebu-uart: document DT bindings for marvell, armada-3700-uart-clock Andrew Lunn
2021-08-02 14:45       ` Pali Rohár
2021-07-17 12:38   ` [PATCH v3 4/5] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-07-17 12:38   ` [PATCH v3 5/5] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-08-02 14:45 ` [PATCH v4 0/6] serial: mvebu-uart: Support for higher baudrates Pali Rohár
2021-08-02 14:45   ` [PATCH v4 1/6] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár
2021-08-02 14:45   ` [PATCH v4 2/6] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-08-02 14:45   ` [PATCH v4 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-08-06  0:30     ` Stephen Boyd
2021-08-06  8:28       ` Pali Rohár
2021-08-12 19:33         ` Stephen Boyd
2021-08-12 20:08           ` Pali Rohár [this message]
2021-08-02 14:45   ` [PATCH v4 4/6] dt-bindings: mvebu-uart: update information about UART clock Pali Rohár
2021-08-02 14:45   ` [PATCH v4 5/6] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-08-02 14:45   ` [PATCH v4 6/6] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-08-09 14:53 ` [PATCH v5 0/6] serial: mvebu-uart: Support for higher baudrates Pali Rohár
2021-08-09 14:53   ` [PATCH v5 1/6] math64: New DIV_U64_ROUND_CLOSEST helper Pali Rohár
2021-08-09 14:53   ` [PATCH v5 2/6] serial: mvebu-uart: implement UART clock driver for configuring UART base clock Pali Rohár
2021-08-09 14:53   ` [PATCH v5 3/6] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock Pali Rohár
2021-08-09 14:53   ` [PATCH v5 4/6] dt-bindings: mvebu-uart: update information about UART clock Pali Rohár
2021-08-09 14:53   ` [PATCH v5 5/6] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it Pali Rohár
2021-08-09 14:53   ` [PATCH v5 6/6] serial: mvebu-uart: implement support for baudrates higher than 230400 Pali Rohár
2021-08-20 17:22   ` [PATCH v5 0/6] serial: mvebu-uart: Support for higher baudrates Pali Rohár
2021-08-31  8:35     ` Pali Rohár
2021-09-21  7:41       ` Greg Kroah-Hartman

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