linux-kernel - Re: [PATCH 1/6] drm/v3d: Document cache flushing ABI.

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Message-ID: <87tvju1h1g.fsf@anholt.net>
Date:   Mon, 03 Dec 2018 12:39:23 -0800
From:   Eric Anholt <eric@...olt.net>
To:     Dave Emett <david.emett@...adcom.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Thomas Spurden <thomas.spurden@...adcom.com>
Subject: Re: [PATCH 1/6] drm/v3d: Document cache flushing ABI.

Dave Emett <david.emett@...adcom.com> writes:

> On Mon, 3 Dec 2018 at 17:22, Dave Emett <david.emett@...adcom.com> wrote:
>>
>> > + * The caches (L1T, slice, and L2T) will be flushed before the job
>> > + * executes.  The TLB writes are guaranteed to have been flushed by
>>
>> I would say before *each* job executes, as the caches are flushed
>> before both bin and render.
>> I wouldn't say "the caches" as not all of the V3D caches are flushed
>> before executing a control list. In particular, the VCD cache is not
>> cleared by the kernel driver (not even sure if there is a register
>> interface to do this); it is expected that the control list will do
>> this itself (using the CLEAR_VCD_CACHE instruction).
>> On 3.3 and earlier there is a separate L2C for instructions/uniforms
>> and a GCA. These do need to be flushed, and it looks like they are, so
>> they should be mentioned here.
>
> Correction: on *3.2* and earlier there is a separate L2C for
> instructions/uniforms. On 3.3 and earlier there is a GCA.
>
> It looks like we're currently unconditionally writing the L2C clear
> registers. We should really only be doing this on 3.2 and earlier.

OK, I've pushed the timeline name and tracing to drm-misc-next, and I'll
resend the rest with more comments and the L2C change and outside-in
invalidation once I'm far enough into this CTS run that I'm confident.

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