linux-kernel - Re: [PATCH] drm/msm/mdp5: Use eariler mixers when possible

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Date:   Fri, 5 Jul 2019 13:24:37 -0600
From:   Jeffrey Hugo <jeffrey.l.hugo@...il.com>
To:     Rob Clark <robdclark@...il.com>
Cc:     Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm/mdp5: Use eariler mixers when possible

On Mon, Jul 1, 2019 at 1:55 PM Rob Clark <robdclark@...il.com> wrote:
>
> On Mon, Jul 1, 2019 at 10:41 AM Jeffrey Hugo <jeffrey.l.hugo@...il.com> wrote:
> >
> > When assigning a mixer, we will iterate through the entire list looking for
> > a suitable match.  This results in selecting the last match.  We should
> > stop at the first match, since lower numbered mixers will typically have
> > more capabilities, and are likely to be what the bootloader used, if we
> > are looking to reuse the bootloader config in future.
>
> I think for matching bootloader config, we need to read it out of the
> hw and do it the hard way, rather than making assumptions.
>
> For picking hwpipe for a plane, I made an effort to pick the available
> hwpipe w/ the *least* capabilities that fit the requirements (ie.
> scaling/yuv/etc) in order to leave the more capable hwpipe available
> for future use.  Not sure if same approach would make sense for
> mixers?  But not sure if picking something that bootloader probably
> also would have picked is a great argument.
>
> I do have some (now ancient) code from db410/mdp5 to read out he hw
> state.. I *think* that might have post-dated dynamically picking
> mixers.  (The older mdp5 on db410c also had to deal with figuring out
> SMP block config, iirc.. thankfully newer mdp5 doesn't have to deal
> with that.)

So I ripped this out and retested as I was looking back at it.  Things
still work.  I probably saw a need for this in the middle of my
hacking, but its clearly not needed anymore so lets drop it for now.