linux-kernel - Re: [PATCH 2/3] drm/msm/dpu: Set DATABUS

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Message-ID: <cce68370-3fd9-4c9a-258e-af0d5d057fda@quicinc.com>
Date:   Fri, 16 Jun 2023 14:18:39 -0700
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Jessica Zhang <quic_jesszhan@...cinc.com>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Marijn Suijten <marijn.suijten@...ainline.org>
CC:     <linux-arm-msm@...r.kernel.org>, <freedreno@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] drm/msm/dpu: Set DATABUS_WIDEN on command mode
 encoders



On 6/14/2023 12:56 AM, Dmitry Baryshkov wrote:
> On 14/06/2023 04:57, Jessica Zhang wrote:
>> Add a DPU INTF op to set the DATABUS_WIDEN register to enable the
>> databus-widen mode datapath.
>>
>> Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c |  3 +++
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c          | 12 ++++++++++++
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.h          |  3 +++
>>   3 files changed, 18 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c 
>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c
>> index b856c6286c85..124ba96bebda 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c
>> @@ -70,6 +70,9 @@ static void _dpu_encoder_phys_cmd_update_intf_cfg(
>>       if (intf_cfg.dsc != 0 && phys_enc->hw_intf->ops.enable_compression)
>>           phys_enc->hw_intf->ops.enable_compression(phys_enc->hw_intf);
>> +
>> +    if (phys_enc->hw_intf->ops.enable_widebus)
>> +        phys_enc->hw_intf->ops.enable_widebus(phys_enc->hw_intf);
> 
> No. Please provide a single function which takes necessary 
> configuration, including compression and wide_bus_enable.
> 

There are two ways to look at this. Your point is coming from the 
perspective that its programming the same register but just a different 
bit. But that will also make it a bit confusing.

So lets say the function is called intf_cfg2_xxx(..., bool widebus, bool 
data_compress)

Now for the caller who wants to just enable widebus this will be

intf_cfg2_xxx(....., true, false)

if we want to do both

intf_cfg2_xxx(...., true, true)

the last one where we want to do just data_compress(highly unlikely and 
not recommended)

intf_cfg2_xxx(...., false, true)

Now someone looking at the code will have to go and find out what each 
bool is.

Whereas with separate ops, its kind of implicit.

For that reason, I dont think this patch is bad at all.