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Message-ID: <31f116f6-a6b7-1241-83bc-96c31e718f3f@linaro.org>
Date:   Tue, 25 Apr 2023 10:54:47 +0300
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Subject: Re: [PATCH v2 3/3] drm/msm/dpu: Pass catalog pointers directly from
 RM instead of IDs
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To:     Marijn Suijten <marijn.suijten@somainline.org>,
        Abhinav Kumar <quic_abhinavk@quicinc.com>
Cc:     Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        ~postmarketos/upstreaming@lists.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@somainline.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Martin Botka <martin.botka@somainline.org>,
        Jami Kettunen <jami.kettunen@somainline.org>,
        Jordan Crouse <jordan@cosmicpenguin.net>,
        linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org,
        freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org
References: <20230418-dpu-drop-useless-for-lookup-v2-0-acb08e82ef19@somainline.org>
 <20230418-dpu-drop-useless-for-lookup-v2-3-acb08e82ef19@somainline.org>
 <50d22e0c-84b3-0678-eb06-30fb66fd24cf@quicinc.com>
 <ymq4kstme55dm3j5kr6trevnwdelhjq7e7m4yky6zcbnf7auid@66l7inxz4oq2>
 <CAA8EJprYQUFER6x1+ucHX_Ze2uqWc6xoEaYDdJ1s0jgZjPJ0QQ@mail.gmail.com>
 <c809476f-74bc-0399-08f9-1bf26e7170fa@quicinc.com>
 <r2tndjr5jbjtrwwti6l3ag7562e53nqx2uk6vz6fx43yc7sncl@eypc37r2ey3j>
From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
In-Reply-To: <r2tndjr5jbjtrwwti6l3ag7562e53nqx2uk6vz6fx43yc7sncl@eypc37r2ey3j>
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On 25/04/2023 10:16, Marijn Suijten wrote:
> On 2023-04-24 16:23:17, Abhinav Kumar wrote:
>>
>>
>> On 4/24/2023 3:54 PM, Dmitry Baryshkov wrote:
>>> On Tue, 25 Apr 2023 at 01:03, Marijn Suijten
>>> <marijn.suijten@somainline.org> wrote:
>>>>
>>>> On 2023-04-21 16:25:15, Abhinav Kumar wrote:
>>>>>
>>>>>
>>>>> On 4/21/2023 1:53 PM, Marijn Suijten wrote:
>>>>>> The Resource Manager already iterates over all available blocks from the
>>>>>> catalog, only to pass their ID to a dpu_hw_xxx_init() function which
>>>>>> uses an _xxx_offset() helper to search for and find the exact same
>>>>>> catalog pointer again to initialize the block with, fallible error
>>>>>> handling and all.
>>>>>>
>>>>>> Instead, pass const pointers to the catalog entries directly to these
>>>>>> _init functions and drop the for loops entirely, saving on both
>>>>>> readability complexity and unnecessary cycles at boot.
>>>>>>
>>>>>> Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
>>>>>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
>>>>>
>>>>> Overall, a nice cleanup!
>>>>>
>>>>> One comment below.
>>>>>
>>>>>> ---
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c        | 37 +++++----------------
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.h        | 14 ++++----
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c        | 32 +++---------------
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.h        | 11 +++----
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dspp.c       | 38 ++++-----------------
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dspp.h       | 12 +++----
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_interrupts.h |  2 +-
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c       | 40 ++++++-----------------
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.h       | 12 +++----
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_lm.c         | 38 ++++-----------------
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_lm.h         | 10 +++---
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_merge3d.c    | 33 +++----------------
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_merge3d.h    | 14 ++++----
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.c   | 33 +++----------------
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_pingpong.h   | 14 ++++----
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp.c       | 39 ++++------------------
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp.h       | 12 +++----
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_vbif.c       | 33 +++----------------
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_vbif.h       | 11 +++----
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_wb.c         | 33 ++++---------------
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_hw_wb.h         | 11 +++----
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c           | 17 +++++-----
>>>>>>     drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c            | 18 +++++-----
>>>>>>     23 files changed, 139 insertions(+), 375 deletions(-)
>>>>>>
>>>>>
>>>>> <snipped>
>>>>>
>>>>>> -struct dpu_hw_intf *dpu_hw_intf_init(enum dpu_intf idx,
>>>>>> -           void __iomem *addr,
>>>>>> -           const struct dpu_mdss_cfg *m)
>>>>>> +struct dpu_hw_intf *dpu_hw_intf_init(const struct dpu_intf_cfg *cfg,
>>>>>> +           void __iomem *addr)
>>>>>>     {
>>>>>>       struct dpu_hw_intf *c;
>>>>>> -   const struct dpu_intf_cfg *cfg;
>>>>>> +
>>>>>> +   if (cfg->type == INTF_NONE) {
>>>>>> +           pr_err("Cannot create interface hw object for INTF_NONE type\n");
>>>>>> +           return ERR_PTR(-EINVAL);
>>>>>> +   }
>>>>>
>>>>> The caller of dpu_hw_intf_init which is the RM already has protection
>>>>> for INTF_NONE, see below
>>>>>
>>>>>            for (i = 0; i < cat->intf_count; i++) {
>>>>>                    struct dpu_hw_intf *hw;
>>>>>                    const struct dpu_intf_cfg *intf = &cat->intf[i];
>>>>>
>>>>>                    if (intf->type == INTF_NONE) {
>>>>>                            DPU_DEBUG("skip intf %d with type none\n", i);
>>>>>                            continue;
>>>>>                    }
>>>>>                    if (intf->id < INTF_0 || intf->id >= INTF_MAX) {
>>>>>                            DPU_ERROR("skip intf %d with invalid id\n",
>>>>> intf->id);
>>>>>                            continue;
>>>>>                    }
>>>>>                    hw = dpu_hw_intf_init(intf->id, mmio, cat);
>>>>>
>>>>> So this part can be dropped.
>>>>
>>>> I mainly intended to keep original validation where _intf_offset would
>>>> skip INTF_NONE, and error out.  RM init is hence expected to filter out
>>>> INTF_NONE instead of running into that `-EINVAL`, which I maintained
>>>> here.
>>>>
>>>> If you think there won't be another caller of dpu_hw_intf_init, and that
>>>> such validation is hence excessive, I can remove it in a followup v3.
>>>
>>> I'd prefer to see the checks at dpu_rm to be dropped.
>>> dpu_hw_intf_init() (and other dpu_hw_foo_init() functions) should be
>>> self-contained. If they can not init HW block (e.g. because the index
>>> is out of the boundaries), they should return an error.
>>>
>>
>> They already do that today because even without this it will call into
>> _intf_offset() and that will bail out for INTF_NONE.
>>
>> I feel this is a duplicated check because the caller with the loop needs
>> to validate the index before passing it to dpu_hw_intf_init() otherwise
>> the loop will get broken at the first return of the error and rest of
>> the blocks will also not be initialized.
> 
> To both: keep in mind that the range-checks we want to remove from
> dpu_rm_init validate the ID (index?) of a block.  This check is for the
> *TYPE* of an INTF block, to skip it gracefully if no hardware is mapped
> there.  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.
> 
> Hence we _should_ keep the graceful TYPE check in dpu_rm_init() to skip
> calling this function _and assigning it to the rm->hw_intf array_.  But
> I can remove the second TYPE check here in dpu_hw_intf_init() if you
> prefer.

We can return NULL from dpu_hw_foo_init(), which would mean that the 
block was skipped or is not present.

> 
> - Marijn

-- 
With best wishes
Dmitry