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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>
From:   Murali Karicheri <m-karicheri2@ti.com>
Message-ID: <f1b689cc-5d1b-0333-7a1c-cb6d58169e12@ti.com>
Date:   Tue, 5 Feb 2019 10:08:11 -0500
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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.

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
>