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Subject: Re: [PATCH v2 01/14] dt-bindings: remoteproc: Add TI PRUSS bindings
To:     Roger Quadros <rogerq@ti.com>, Tony Lindgren <tony@atomide.com>,
        <s-anna@ti.com>
CC:     <ohad@wizery.com>, <bjorn.andersson@linaro.org>,
        <david@lechnology.com>, <nsekhar@ti.com>, <t-kristo@ti.com>,
        <nsaulnier@ti.com>, <jreeder@ti.com>, <woods.technical@gmail.com>,
        <linux-omap@vger.kernel.org>, <linux-remoteproc@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <devicetree@vger.kernel.org>
References: <1549290167-876-1-git-send-email-rogerq@ti.com>
 <1549290167-876-2-git-send-email-rogerq@ti.com>
 <20190204163312.GI5720@atomide.com> <5C5959DB.2090608@ti.com>
 <f1b689cc-5d1b-0333-7a1c-cb6d58169e12@ti.com> <5C59AEA3.1080400@ti.com>
From:   Murali Karicheri <m-karicheri2@ti.com>
Message-ID: <124e9f09-fb60-071d-e2ba-ec6f7fb3955c@ti.com>
Date:   Tue, 5 Feb 2019 11:15:13 -0500
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Roger,

On 02/05/2019 10:41 AM, Roger Quadros wrote:
> Murali,
> 
> On 05/02/19 17:08, Murali Karicheri wrote:
>> Hi Roger,
>>
>> On 02/05/2019 04:39 AM, Roger Quadros wrote:
>>> Hi Tony & Suman,
>>>
>>> On 04/02/19 18:33, Tony Lindgren wrote:
>>>> Hi,
>>>>
>>>> * Roger Quadros <rogerq@ti.com> [190204 14:23]:
>>>>> From: Suman Anna <s-anna@ti.com>
>>>> ...
>>>>> +Example:
>>>>> +========
>>>>> +1.    /* AM33xx PRU-ICSS */
>>>>> +
>>>>> +    pruss: pruss@0 {
>>>>> +        compatible = "ti,am3356-pruss";
>>>>> +        reg = <0x0 0x2000>,
>>>>> +              <0x2000 0x2000>,
>>>>> +              <0x10000 0x3000>;
>>>>> +        reg-names = "dram0", "dram1",
>>>>> +                "shrdram2";
>>>>> +        #address-cells = <1>;
>>>>> +        #size-cells = <1>;
>>>>> +        ranges;
>>>>
>>>> Thanks for fixing up the reg ranges for the top level node.
>>>>
>>>> Ideally there would not even be a top level node here as
>>>> AFAIK the whole PRUSS is a collection of devices on a PRU
>>>> internal interconnect. So following that path a bit further..
>>>> How about just get rid of the top level node and just do:
>>>>
>>>> pruss: pruss@0 {
>>>>      dram0: memory@0 {
>>>>             device_type = "memory";
>>>>             reg = <0x0 0x2000>;
>>>>      };
>>>>
>>>>      dram1: memory@2000 {
>>>>             device_type = "memory";
>>>>             reg = <0x2000 0x2000>;
>>>>      };
>>>
>>> Actually dram0 and dram1 are data memories for PRU0 and PRU1 respectively.
>>> Isn't it better if they are moved to the pru node?
>>> e.g.
>>>
>>>      pru0: pru@34000 {
>>>          compatible = "ti,am3356-pru";
>>>          reg = <0x34000 0x2000>,
>>>                <0x22000 0x400>,
>>>                <0x22400 0x100>,
>>>                <0x0     0x2000>;
>>>          reg-names = "iram", "control", "debug", "dram";
>>>          ...
>>>      };
>>>
>>>      pru1: pru@38000 {
>>>          compatible = "ti,am3356-pru";
>>>          reg = <0x38000 0x2000>,
>>>                <0x24000 0x400>,
>>>                <0x24400 0x100>,
>>>                <0x2000  0x2000>;
>>>          reg-names = "iram", "control", "debug", "dram";
>>>          ...
>>>      };
>>>
>>> I think it is better to place a restriction that firmware on PRU0 cannot use data
>>> memory of PRU1 and vice versa.
>>>
>> That will not work as there are switch firmware cases where PRU access
>> DRAM of other PRU and is a valid case to support in the future. So let
>> us not do that.
> 
> PRU firmware accessing DRAM of other PRU is a design contract and that use case
> requires both PRUs to be loaded with matching firmware. That should continue to work.
> 
> What I'm suggesting here is that kernel remoteproc driver should have nothing to do
> with the other PRU's data RAM.
> 
> The application driver if needs both PRUs then it can obviously access both DRAMs
> as it has a phandle to both PRUs.
> 
That should be fine.

Regards,
Murali

> cheers,
> -roger
> 
>>
>> Murali
>>> Application drivers do sometimes need to read/write to data memory. The pru_rproc
>>> driver could provide a API for the application drivers to get virtual address of
>>> the respective PRU's data memory.
>>>
>>>>
>>>>      shrdram2: memory@10000 {
>>>>          device_type = "memory";
>>>>          reg = <0x10000 0x3000>;
>>>>      };
>>>
>>> Shared RAM is not so straight forward. Both PRU firmwares and both application drivers
>>> might need to read/write here. The area split is decided by firmware design and there
>>> is no hardware protection to prevent from stomping on each others toes.
>>>
>>> We need a carveout based memory allocator at least I think that can do a
>>> allocate(base_offset, size); into shared RAM.
>>>
>>> This could be used by pru_rproc driver at firmware load time and by application drivers
>>> at initialization time.
>>>
>>> Thoughts?
>>>
>>>>
>>>>      pruss_cfg: cfg@26000 {
>>>>          ...
>>>>      };
>>>>      ...
>>>> };
>>>>
>>>> If the device_type = "memory" cannot be used here for
>>>> being specific to the top level properties, then
>>>> there's probably some other generic property usable
>>>> here :)
>>>>
>>>>> +        pruss_mii_rt: mii_rt@32000 {
>>>>> +            reg = <0x32000 0x58>;
>>>>> +        };
>>>>
>>>> The node name should not have underscores so
>>>> pruss_mii_rt: mii-rt@32000. Please check the others
>>>> too, like app_node.
>>>>
>>>
>>> OK.
>>>
>>>>> +    app_node: app_node {
>>>>> +        prus = <&pru0>, <&pru1>;
>>>>> +        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>;
>>>>> +    }
>>>>
>>>> If the ti,pruss-gp-mux-sel and ti,pru-interrupt-map are
>>>> firmware configuration options, maybe leave them out of
>>>> the dts completely and make the app-node optional.
>>>
>>> Yes the app-node is optional. I will mention it.
>>>
>>> No, ti,pruss-gp-mux-sel and ti,pru-interrupt-map are not firmware options.
>>> But these settings are application/firmware specific.
>>>
>>> ti,pru-interrupt-map specifies the configuration to be used for the INTC interrupt
>>> controller.
>>>
>>> ti,pruss-gp-mux-sel is used to configure this register.
>>> "Table 30-20. PRUSS_GPCFG0" in http://www.tij.co.jp/jp/lit/ug/spruhz7h/spruhz7h.pdf
>>> "29:26 PR1_PRU0_GP_MUX_SEL"
>>>
>>> It configures how the pins from the PRUSS module are routed internally
>>> to the various modules.
>>>
>>> see "30.2.1 PRU-ICSS I/O Interface"
>>> and "Table 30-1. PRU-ICSS1 I/O Signals"
>>>
>>>>
>>>> And have a proper compatible for this node such as
>>>> "ti,pruss-app-xyz". And this should be only set if the the
>>>> hardware is wired up in such way that things need to be
>>>> configured in the dts rather than by the firmware.
>>>
>>> Yes, compatible is a required property as we need to load
>>> the appropriate application (kernel space) driver for it.
>>> I will fix the example.
>>>
>>>>
>>>> And then you can just hide mux-sel and interrupt-map
>>>> behind the compatible property for that hardware. And
>>>> leave them out from the dts and have the handling driver
>>>> would set mux-sel and interrupt-map based on the
>>>> match->data during probe.
>>>
>>> To summarize:
>>>
>>> I'll mark the app node as optional. Only required if a kernel
>>> driver is required for the application.
>>> Compatible is mandatory for app node.
>>> ti,pruss-gp-mux-sel and ti,pru-interrupt-map are optional
>>> for app node.
>>>
>>> cheers,
>>> -roger
>>>
>