Message-ID: <5BFFBA5F.703@ti.com>
Date:   Thu, 29 Nov 2018 12:07:27 +0200
From:   Roger Quadros <rogerq@...com>
To:     David Lechner <david@...hnology.com>, <ohad@...ery.com>,
        <bjorn.andersson@...aro.org>
CC:     <tony@...mide.com>, <robh+dt@...nel.org>, <bcousson@...libre.com>,
        <ssantosh@...nel.org>, <s-anna@...com>, <nsekhar@...com>,
        <t-kristo@...com>, <nsaulnier@...com>, <jreeder@...com>,
        <m-karicheri2@...com>, <woods.technical@...il.com>,
        <linux-omap@...r.kernel.org>, <linux-remoteproc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH 12/16] dt-bindings: remoteproc: ti-pruss: Document
 application node bindings

On 27/11/18 01:27, David Lechner wrote:
> On 11/26/18 1:52 AM, Roger Quadros wrote:
>> From: Tero Kristo <t-kristo@...com>
>>
>> Add documentation for the Texas Instruments PRU application nodes.
>> These are used to configure specific user applications for PRU instances.
> 
> Could this be made into a generic remoteproc producer/consumer binding? Or
> are there really things that are specific to the TI PRU that need to be
> handled?

The remoteproc handle and firmware name sound generic enough.
But there are TI PRU specific properties as well which we'll discuss if
they can be made generic.

> 
>>
>> Signed-off-by: Tero Kristo <t-kristo@...com>
>> [s-anna@...com: some binding updates]
>> Signed-off-by: Suman Anna <s-anna@...com>
>> Signed-off-by: Roger Quadros <rogerq@...com>
>> ---
>>   .../devicetree/bindings/soc/ti/ti,pruss.txt        | 43 ++++++++++++++++++++++
>>   1 file changed, 43 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/soc/ti/ti,pruss.txt b/Documentation/devicetree/bindings/soc/ti/ti,pruss.txt
>> index 3e5f32f..94c91ee 100644
>> --- a/Documentation/devicetree/bindings/soc/ti/ti,pruss.txt
>> +++ b/Documentation/devicetree/bindings/soc/ti/ti,pruss.txt
>> @@ -210,6 +210,38 @@ used in TI Davinci SoCs. Please refer to the corresponding binding document,
>>   Documentation/devicetree/bindings/net/davinci-mdio.txt for details.
>>     +Application/User Nodes
>> +=======================
> 
> Are these supposed to be stand-alone platform devices?
> 

Yes. The first use case we're going to address is the Ethernet ports on the IDKs.
(Industrial development Kit) http://www.ti.com/tool/TMDXIDK437X

>> +A PRU application/user node typically uses one or more PRU device nodes to
>> +implement a PRU application/functionality. Each application/client node would
>> +need a reference to at least a PRU node, and optionally pass some configuration
>> +parameters.
> 
> I thought device tree is not supposed to be used for configuration.

I think we need to word it properly. It is really a hardware/firmware map.
> 
>> +
>> +Required Properties:
>> +--------------------
>> +- prus                 : phandles to the PRU nodes used
>> +
>> +Optional Properties:
>> +--------------------
>> +- firmware-name        : firmwares for the PRU cores, the default firmware
>> +                         for the core from the PRU node will be used if not
>> +                         provided. The firmware names should correspond to
>> +                         the PRU cores listed in the 'prus' property
> 
> Perhaps this should be a "compatible" property instead of "firmware-name"? The
> driver that matches the compatible string can then set the firmware names.

Compatible property is there to choose the application driver. Should have mentioned
it in Required properties.

It is tricky for the driver to decipher the firmware-name as it needs to support
the same use case on multiple platforms and the firmware name will be different for each.
The driver itself is platform agnostic.

So providing the firmware-name in the DT is the easiest and scalable solution.
> 
>> +- ti,pruss-gp-mux-sel  : array of values for the GP_MUX_SEL under PRUSS_GPCFG
>> +                         register for a PRU. This selects the internal muxing
>> +                         scheme for the PRU instance. If not provided, the
>> +                         default out-of-reset value (0) for the PRU core is
>> +                         used. Values should correspond to the PRU cores listed
>> +                         in the 'prus' property
> 
> Is this supposed to be a pinmux? So maybe we should be using pinmux bindings?

We already have pinmux binding for the PRU pins. This GP mux setting is an odd duck.

It provides a way for a set of signals inside the ICSS to be connected to the PRU pins
on the SOC, which are again multiplexed with other SOC pins via the regular pinmux.

Some of the sets are

GPIO mode (0)
EnDAT mode (1)
SD mode (3)
MII2 mode (4)

The application node needs to decide which set it wants to use.

> 
>> +- ti,pru-interrupt-map : PRU interrupt mappings, containing an array of entries
>> +                         with each entry consisting of 4 cell-values. First one
>> +                         is an index towards the "prus" property to identify the
>> +                         PRU core for the interrupt map, second is the PRU
>> +                         System Event id, third is the PRU interrupt channel id
>> +                         and fourth is the PRU host interrupt id. If provided,
>> +                         this map will supercede any other configuration
>> +                         provided through firmware
> 
> Could this mapping just be cells of the interrupt consumer nodes instead of an
> extra property? As I mentioned in a reply to another patch, unless there is a
> compelling reason to do otherwise, the channel to host mapping can be required
> to be 1:1 as recommended in the TRMs, so that cell can be omitted. Also, since
> the interrupt controller is independent of the PRU cores, the cell specifying the
> index of the PRU core is not needed in this case. The #interrupt-cells already
> includes a cell for the system event number, so this just leaves one cell, the
> host channel, to be added to the #interrupt-cells.
> 
> So, instead of:
> 
>     ti,pru-interrupt-map = <0 16 2 7 >, <1 19 1 3>;
> 
> we could have:
> 
>     interrupt-parent = <&pruss_intc>;
>     interrupts = <16 7>, <19 3>;
> 

No, interrupts property will be used to provide the actual sysevent IRQs to the
application driver. Below is how the ethernet application node looks like.

	pruss2_eth {
		compatible = "ti,am57-prueth";
		prus = <&pru2_0>, <&pru2_1>;
		firmware-name = "ti-pruss/am57xx-pru0-prueth-fw.elf",
				"ti-pruss/am57xx-pru1-prueth-fw.elf";
		sram = <&ocmcram1>;
		interrupt-parent = <&pruss2_intc>;
		mii-rt = <&pruss2_mii_rt>;
		iep = <&pruss2_iep>;

		pruss2_emac0: ethernet-mii0 {
			phy-handle = <&pruss2_eth0_phy>;
			phy-mode = "mii";
			interrupts = <20>, <22>;
			interrupt-names = "rx", "tx";
		};

		pruss2_emac1: ethernet-mii1 {
			phy-handle = <&pruss2_eth1_phy>;
			phy-mode = "mii";
			interrupts = <21>, <23>;
			interrupt-names = "rx", "tx";
		};
	};

You can see that interrupts is providing the RX and TX sysevents.

There needs to be a different way to provide the internal INTC map.

Currently there are 2 ways of providing the INTC map. One is via the
resource table and other is via DT.

> There are also already alternate interrupt bindings that allow for the case
> where there is more than one interrupt-parent.
> 
>> +
>>   Example:
>>   ========
>>   1.    /* AM33xx PRU-ICSS */
>> @@ -397,3 +429,14 @@ Example:
>>               ...
>>           };
>>       };
>> +
>> +3:    /* PRU application node example */
>> +    app_node: app_node {
>> +        prus = <&pru1_0>, <&pru1_1>;
>> +        firmware-name = "pruss-app-fw", "pruss-app-fw-2";
>> +        ti,pruss-gp-mux-sel = <2>, <1>;
>> +        /* setup interrupts for prus:
>> +           prus[0] => pru1_0: ev=16, chnl=2, host-irq=7,
>> +           prus[1] => pru1_1: ev=19, chnl=1, host-irq=3 */
>> +        ti,pru-interrupt-map = <0 16 2 7 >, <1 19 1 3>;
>> +    }
>>
> 

cheers,
-roger
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