linux-kernel - Re: [Freedreno] [PATCH v2 3/3] drm/msm/dpu: Pass catalog pointers directly from RM instead of IDs

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Date:   Wed, 26 Apr 2023 00:35:47 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        freedreno@...ts.freedesktop.org,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        David Airlie <airlied@...il.com>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Jordan Crouse <jordan@...micpenguin.net>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Clark <robdclark@...il.com>,
        Martin Botka <martin.botka@...ainline.org>,
        ~postmarketos/upstreaming@...ts.sr.ht,
        Daniel Vetter <daniel@...ll.ch>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Sean Paul <sean@...rly.run>
Subject: Re: [Freedreno] [PATCH v2 3/3] drm/msm/dpu: Pass catalog pointers
 directly from RM instead of IDs

On 2023-04-25 14:32:51, Abhinav Kumar wrote:
<snip>
> >>>>> We can return NULL from dpu_hw_foo_init(), which would mean that the
> >>>>> block was skipped or is not present.
> >>>>
> >>>> An then replace the `if INTF_NONE continue` logic in dpu_rm_init with a
> >>>> check for NULL that skips, and a check for IS_ERR` that goes to `fail`?
> >>>
> >>> You can just drop the INTF_NONE in dpu_rm. If dpu_hw_intf_init()
> >>> returns NULL, the rest of the code in dpu_rm will work correctly.

Sure, I'll keep the check exclusively in dpu_hw_intf_init().  Should I
also move the pingpong==PINGPONG_MAX check into dpu_hw_lm_init()?

> >> The only thing lost will be that the loop in the RM will break at the
> >> first instance of NULL so if the loop has valid intf blocks later, those
> >> will also not get initialized.
> >
> > No, it won't. There is the IS_ERR check, not the IS_ERR_OR_NULL()

Only DSC currently uses IS_ERR_OR_NULL... We should fix that as
rc=PTR_ERR(hw) on the next should be 0 (actually, the intent is for it
to be undefined I think) for that...

> Ack, but isnt that an issue since rm->hw_intf[intf->id - INTF_0] can be 
> assigned to a NULL hw.

Yes, that is exactly the intent here.

> >> That wont happen today because catalog doesnt have such entries but just
> >> wanted to note what gets lost with this change.

It does, we have a few SoCs with type=INTF_NONE.  Quoting myself from
above:

    As per the first patch of this series SM6115/QCM2290 only have a DSI
    interface which always sits at ID 1, and ID 0 has its TYPE set to
    INTF_NONE and is skipped.

- Marijn