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Subject: Re: [PATCH v2 01/14] dt-bindings: remoteproc: Add TI PRUSS bindings
To:     Tony Lindgren <tony@atomide.com>, <s-anna@ti.com>
References: <1549290167-876-1-git-send-email-rogerq@ti.com>
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 <20190204163312.GI5720@atomide.com>
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        <woods.technical@gmail.com>, <linux-omap@vger.kernel.org>,
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From:   Roger Quadros <rogerq@ti.com>
Message-ID: <5C5959DB.2090608@ti.com>
Date:   Tue, 5 Feb 2019 11:39:39 +0200
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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.

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

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