linux-kernel - Re: [PATCH 04/10] gpu: host1x: Lock classes during job submission

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Date:   Tue, 5 Dec 2017 16:43:27 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Mikko Perttunen <cyndis@...si.fi>,
        Mikko Perttunen <mperttunen@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com
Cc:     dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/10] gpu: host1x: Lock classes during job submission

On 05.12.2017 16:21, Mikko Perttunen wrote:
> On 07.11.2017 23:23, Dmitry Osipenko wrote:
>> On 07.11.2017 15:28, Mikko Perttunen wrote:
>>> On 05.11.2017 18:46, Dmitry Osipenko wrote:
>>>> On 05.11.2017 14:01, Mikko Perttunen wrote:
>>>>> ...
>>>>>
>>>>> +static int mlock_id_for_class(unsigned int class)
>>>>> +{
>>>>> +#if HOST1X_HW >= 6
>>>>> +    switch (class)
>>>>> +    {
>>>>> +    case HOST1X_CLASS_HOST1X:
>>>>> +        return 0;
>>>>> +    case HOST1X_CLASS_VIC:
>>>>> +        return 17;
>>>>
>>>> What is the meaning of returned ID values that you have defined here? Why VIC
>>>> should have different ID on T186?
>>>
>>> On T186, MLOCKs are not "generic" - the HW knows that each MLOCK corresponds to
>>> a specific class. Therefore we must map that correctly.
>>>
>>
>> Okay.
>>
>>>>
>>>>> +    default:
>>>>> +        return -EINVAL;
>>>>> +    }
>>>>> +#else
>>>>> +    switch (class)
>>>>> +    {
>>>>> +    case HOST1X_CLASS_HOST1X:
>>>>> +        return 0;
>>>>> +    case HOST1X_CLASS_GR2D:
>>>>> +        return 1;
>>>>> +    case HOST1X_CLASS_GR2D_SB:
>>>>> +        return 2;
>>>>
>>>> Note that we are allowing to switch 2d classes in the same jobs context and
>>>> currently jobs class is somewhat hardcoded to GR2D.
>>>>
>>>> Even though that GR2D and GR2D_SB use different register banks, is it okay to
>>>> trigger execution of different classes simultaneously? Would syncpoint
>>>> differentiate classes on OP_DONE event?
>>>
>>> Good point, we might need to use the same lock for these two.
>>>
>>>>
>>>> I suppose that MLOCK (the module lock) implies the whole module locking,
>>>> wouldn't it make sense to just use the module ID's defined in the TRM?
>>>
>>> Can you point out where these are defined?
>>
>> See INDMODID / REGF_MODULEID fields of HOST1X_CHANNEL_INDOFF2_0 /
>> HOST1X_SYNC_REGF_ADDR_0 registers, bit numbers of HOST1X_SYNC_INTSTATUS_0 /
>> HOST1X_SYNC_INTC0MASK_0 / HOST1X_SYNC_MOD_TEARDOWN_0.
> 
> These values look like they would work on T20, but at least on T124 the module
> numbering for modules we want to lock goes above the number of MLOCKs so the
> indexing scheme would not work there..
> 

Indeed, for some reason I was thinking that there are 32 MLOCK's instead of 16.