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Date: Fri, 13 Oct 2017 14:26:43 -0500
From: Rob Herring <robh@...nel.org>
To: srinivas.kandagatla@...aro.org
Cc: gregkh@...uxfoundation.org, broonie@...nel.org,
alsa-devel@...a-project.org, sdharia@...eaurora.org, bp@...e.de,
poeschel@...onage.de, treding@...dia.com,
gong.chen@...ux.intel.com, andreas.noever@...il.com,
alan@...ux.intel.com, mathieu.poirier@...aro.org, daniel@...ll.ch,
jkosina@...e.cz, sharon.dvir1@...l.huji.ac.il, joe@...ches.com,
davem@...emloft.net, james.hogan@...tec.com,
michael.opdenacker@...e-electrons.com, pawel.moll@....com,
mark.rutland@....com, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, kheitke@...ience.com,
linux-arm-msm@...r.kernel.org, arnd@...db.de
Subject: Re: [Patch v6 1/7] slimbus: Device management on SLIMbus
On Fri, Oct 06, 2017 at 05:51:30PM +0200, srinivas.kandagatla@...aro.org wrote:
> From: Sagar Dharia <sdharia@...eaurora.org>
>
> SLIMbus (Serial Low Power Interchip Media Bus) is a specification
> developed by MIPI (Mobile Industry Processor Interface) alliance.
> SLIMbus is a 2-wire implementation, which is used to communicate with
> peripheral components like audio-codec.
> SLIMbus uses Time-Division-Multiplexing to accommodate multiple data
> channels, and control channel. Control channel has messages to do
> device-enumeration, messages to send/receive control-data to/from
> slimbus devices, messages for port/channel management, and messages to
> do bandwidth allocation.
> The framework supports multiple instances of the bus (1 controller per
> bus), and multiple slave devices per controller.
>
> This patch does device enumeration, logical address assignment,
> informing device when the device reports present/absent etc.
> Reporting present may need the driver to do the needful (e.g. turning
> on voltage regulators powering the device). Additionally device is
> probed when it reports present if that device doesn't need any such
> steps mentioned above.
>
> Signed-off-by: Sagar Dharia <sdharia@...eaurora.org>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> ---
> Documentation/devicetree/bindings/slimbus/bus.txt | 57 ++
Split to separate patch.
> Documentation/slimbus/summary | 109 ++++
> drivers/Kconfig | 2 +
> drivers/Makefile | 1 +
> drivers/slimbus/Kconfig | 11 +
> drivers/slimbus/Makefile | 5 +
> drivers/slimbus/slim-core.c | 695 ++++++++++++++++++++++
> include/linux/mod_devicetable.h | 13 +
> include/linux/slimbus.h | 299 ++++++++++
> 9 files changed, 1192 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/slimbus/bus.txt
> create mode 100644 Documentation/slimbus/summary
> create mode 100644 drivers/slimbus/Kconfig
> create mode 100644 drivers/slimbus/Makefile
> create mode 100644 drivers/slimbus/slim-core.c
> create mode 100644 include/linux/slimbus.h
>
> diff --git a/Documentation/devicetree/bindings/slimbus/bus.txt b/Documentation/devicetree/bindings/slimbus/bus.txt
> new file mode 100644
> index 0000000..cb658bb
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/slimbus/bus.txt
> @@ -0,0 +1,57 @@
> +SLIM(Serial Low Power Interchip Media Bus) bus
> +
> +SLIMbus is a 2-wire bus, and is used to communicate with peripheral
> +components like audio-codec.
> +
> +Controller is a normal device using binding for whatever bus it is
> +on (e.g. platform bus).
I can't have a PCI based slimbus controller? "platform bus" is a
Linuxism.
> +Required property for SLIMbus controller node:
> +- compatible - name of SLIMbus controller following generic names
> + recommended practice.
generic names aren't recommended. Allowed with some conditons, yes.
> +- #address-cells - should be 2
You used 4 for your controller.
> +- #size-cells - should be 0
> +
> +No other properties are required in the SLIMbus controller bus node.
That's not a useful statement. Almost every controller probably has
other required properties.
> +
> +Child nodes:
> +Every SLIMbus controller node can contain zero or more child nodes
> +representing slave devices on the bus. Every SLIMbus slave device is
> +uniquely determined by the enumeration address containing 4 fields:
> +Manufacturer ID, Product code, Device index, and Instance value for
> +the device.
> +If child node is not present and it is instantiated after device
> +discovery (slave device reporting itself present).
> +
> +In some cases it may be necessary to describe non-probeable device
> +details such as non-standard ways of powering up a device. In
> +such cases, child nodes for those devices will be present as
> +slaves of the slimbus-controller, as detailed below.
> +
> +Required property for SLIMbus child node if it is present:
> +- reg - Is Duplex (Device index, Instance ID) from Enumeration
> + Address.
> + Device Index Uniquely identifies multiple Devices within
> + a single Component.
> + Instance ID Is for the cases where multiple Devices of the
> + same type or Class are attached to the bus.
> +
> +- compatible -"slimMID,PID". The textual representation of Manufacturer ID,
> + Product Code, shall be in lower case hexadecimal with leading
> + zeroes suppressed
> +
> +SLIMbus example for Qualcomm's slimbus manager component:
> +
> + slim@...80000 {
> + compatible = "qcom,slim-msm";
> + reg = <0x28080000 0x2000>,
> + interrupts = <0 33 0>;
> + clocks = <&lcc SLIMBUS_SRC>, <&lcc AUDIO_SLIMBUS_CLK>;
> + clock-names = "iface_clk", "core_clk";
> + #address-cells = <2>;
> + #size-cells = <0>;
> +
> + codec: wcd9310@1{
Is '1' by itself unique enough because you have 2 address cells. The
unit-address is typically split up into fields with commas unless it's
just a memory address. Anyway, you need to define the unit address
format in this doc.
> + compatible = "slim217,60"";
> + reg = <1 0>;
> + };
> + };
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