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Date: Tue, 5 Feb 2019 11:15:13 -0500
From: Murali Karicheri <m-karicheri2@...com>
To: Roger Quadros <rogerq@...com>, Tony Lindgren <tony@...mide.com>,
<s-anna@...com>
CC: <ohad@...ery.com>, <bjorn.andersson@...aro.org>,
<david@...hnology.com>, <nsekhar@...com>, <t-kristo@...com>,
<nsaulnier@...com>, <jreeder@...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 v2 01/14] dt-bindings: remoteproc: Add TI PRUSS bindings
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@...com> [190204 14:23]:
>>>>> From: Suman Anna <s-anna@...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@...0 {
>>>> 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@...00 {
>>> compatible = "ti,am3356-pru";
>>> reg = <0x34000 0x2000>,
>>> <0x22000 0x400>,
>>> <0x22400 0x100>,
>>> <0x0 0x2000>;
>>> reg-names = "iram", "control", "debug", "dram";
>>> ...
>>> };
>>>
>>> pru1: pru@...00 {
>>> 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@...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?
>>>
>>>>
>>>> pruss_cfg: cfg@...00 {
>>>> ...
>>>> };
>>>> ...
>>>> };
>>>>
>>>> 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@...00 {
>>>>> + reg = <0x32000 0x58>;
>>>>> + };
>>>>
>>>> The node name should not have underscores so
>>>> pruss_mii_rt: mii-rt@...00. 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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