linux-kernel - Re: [PATCH 1/3] drm/msm/disp/dpu1: allow reservation even if dspps are not available.

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Message-ID: <84849b99-93ab-bc10-39ff-ac46328ede47@linaro.org>
Date:   Tue, 17 Jan 2023 18:40:11 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Kalyan Thota <quic_kalyant@...cinc.com>,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, robdclark@...omium.org,
        dianders@...omium.org, swboyd@...omium.org,
        quic_vpolimer@...cinc.com, quic_abhinavk@...cinc.com
Subject: Re: [PATCH 1/3] drm/msm/disp/dpu1: allow reservation even if dspps
 are not available.

On 17/01/2023 18:35, Dmitry Baryshkov wrote:
> On 17/01/2023 18:21, Kalyan Thota wrote:
>> if any topology requests for dspps and catalogue doesn't have the
>> allocation, avoid failing the reservation.
>>
>> This can pave way to build logic allowing composer fallbacks
>> for all the color features that are handled in dspp.
>>
>> Signed-off-by: Kalyan Thota <quic_kalyant@...cinc.com>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 8 +++++++-
>>   1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c 
>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
>> index 73b3442..c8899ae 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
>> @@ -343,7 +343,13 @@ static bool 
>> _dpu_rm_check_lm_and_get_connected_blks(struct dpu_rm *rm,
>>           return true;
>>       idx = lm_cfg->dspp - DSPP_0;
>> -    if (idx < 0 || idx >= ARRAY_SIZE(rm->dspp_blks)) {
>> +
>> +    if (idx < 0) {
> 
> The change doesn't correspond to commit message.
> 
>> +        DPU_DEBUG("lm doesn't have dspp, ignoring the request %d\n", 
>> lm_cfg->dspp);
>> +        return true;
>> +    }
>> +
>> +    if (idx >= ARRAY_SIZE(rm->dspp_blks)) {
>>           DPU_ERROR("failed to get dspp on lm %d\n", lm_cfg->dspp);
>>           return false;
>>       }
> 
> If you'd like to remove duplicate for the (idx >= ARRAY_SIZE) check, I'd 
> suggest dropping the second one
> 

I've misread the patch. However I don't see, why would one request 
DSPP_NONE while specifying topology->num_dspp. I think that you are 
trying to put additional logic into a function that should just check 
for the available resources.

-- 
With best wishes
Dmitry