linux-kernel - Re: [PATCH v2 01/14] dt-bindings: remoteproc: Add TI PRUSS bindings

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Date:   Wed, 13 Feb 2019 21:01:48 -0600
From:   Suman Anna <s-anna@...com>
To:     Tony Lindgren <tony@...mide.com>, Roger Quadros <rogerq@...com>
CC:     <ohad@...ery.com>, <bjorn.andersson@...aro.org>,
        <david@...hnology.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>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v2 01/14] dt-bindings: remoteproc: Add TI PRUSS bindings

On 2/5/19 10:41 AM, Tony Lindgren wrote:
> * Roger Quadros <rogerq@...com> [190205 09:40]:
>> On 04/02/19 18:33, Tony Lindgren wrote:
>>>
>>> 	shrdram2: memory@...00 {
>>> 		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?
> 
> That sounds sane to me :)
> 
>>> 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.
> 
> OK. So just to see if we have a standard solution available already..
> It sounds a bit similar to what we're doing with omap-wakeupgen.c
> and stacked interrupts? I wonder if something similar might help
> here?
> 
>> 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.

Actually, that's not entirely accurate. This is an internal pinmux (not
controllable per pin, but rather dictates a different sets of groups of
pins at the PRUSS boundary, which are then again multiplexed at the SoC
level using the standard padconf/pinmux. It is a single register per
core into which you can set some values between 0 through 4 IIRC
(unfortunately the values are also not uniform across the various SoCs).

regards
Suman

>>
>> see "30.2.1 PRU-ICSS I/O Interface"
>> and "Table 30-1. PRU-ICSS1 I/O Signals"
> 
> Well these are external signals for PRUSS processor (although not
> necessarily external signals for the SoC). So why not handle them
> with a standard pinctlr binding with #pinctrl-cells?
> 
> Sure it may not even be the Linux pinctrl framework running on the
> main SoC handling these pins, but after all you're describing
> hardware for a processor. Maybe Linus W has some comments on this?
> 
> Regards,
> 
> Tony
>