linux-kernel - Re: [PATCH v2] drm/msm/dpu: always program dsc active bits

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Message-ID: <c09725ff-771c-35d1-adc9-4bb1b7c1c334@quicinc.com>
Date:   Fri, 14 Apr 2023 11:55:41 -0700
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     Marijn Suijten <marijn.suijten@...ainline.org>
CC:     Kuogee Hsieh <quic_khsieh@...cinc.com>, <robdclark@...il.com>,
        <sean@...rly.run>, <swboyd@...omium.org>, <dianders@...omium.org>,
        <vkoul@...nel.org>, <daniel@...ll.ch>, <airlied@...il.com>,
        <agross@...nel.org>, <dmitry.baryshkov@...aro.org>,
        <andersson@...nel.org>, <quic_sbillaka@...cinc.com>,
        <freedreno@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drm/msm/dpu: always program dsc active bits



On 4/14/2023 10:28 AM, Marijn Suijten wrote:
> On 2023-04-14 08:41:37, Abhinav Kumar wrote:
>>
>> On 4/14/2023 12:48 AM, Marijn Suijten wrote:
>>> Capitalize DSC in the title, as discussed in v1.
>>>
>>> On 2023-04-13 08:56:41, Kuogee Hsieh wrote:
>>>> In current code, the DSC active bits are written only if cfg->dsc is set.
>>>> However, for displays which are hot-pluggable, there can be a use-case
>>>> of disconnecting a DSC supported sink and connecting a non-DSC sink.
>>>>
>>>> For those cases we need to clear DSC active bits during tear down.
>>>>
>>>> Changes in V2:
>>>> 1) correct commit text as suggested
>>>> 2) correct Fixes commit id
>>>> 3) add FIXME comment
>>>>
>>>> Fixes: 77f6da90487c ("drm/msm/disp/dpu1: Add DSC support in hw_ctl")
>>>> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
>>>> Reviewed-by: Marijn Suijten <marijn.suijten@...ainline.org>
>>>
>>> By default git send-email should pick this up in the CC line...  but I
>>> had to download this patch from lore once again.
>>>
>>
>> Yes, I think what happened here is, he didnt git am the prev rev and
>> make changes on top of that so git send-email didnt pick up. We should
>> fix that process.
> 
> The mail was sent so it must have gone through git send-email, unless a
> different mail client was used to send the .patch file.  I think you are
> confusing this with git am (which doesn't need to be used if editing a
> commit on a local branch) and subsequently git format-patch, which takes
> a commit from a git repository and turns it into a .patch file: neither
> of these "converts" r-b's (and other tags) to cc, that's happening in
> git send-email (see `--suppress-cc` documentation in `man
> git-send-email`).
> 

Yes, ofcourse git send-email was used to send the patch, not any other 
mail client.

Yes i am also aware that send-email converts rb to CC.

But if you keep working on the local branch, then you would have to 
manually add the r-bs. If you use am of the prev version and develop on 
that, it will automatically add the r-bs.


> I can recommend b4: it has lots of useful features including
> automatically picking up reviews and processing revisions.  It even
> requires a changelog to be edited ;).  However, finding the right flags
> and trusting it'll "do as ordered" is a bit daunting at first.
> 
>>>> ---
>>>>    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c | 8 ++++----
>>>>    1 file changed, 4 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c
>>>> index bbdc95c..1651cd7 100644
>>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c
>>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c
>>>> @@ -541,10 +541,10 @@ static void dpu_hw_ctl_intf_cfg_v1(struct dpu_hw_ctl *ctx,
>>>>    	if (cfg->merge_3d)
>>>>    		DPU_REG_WRITE(c, CTL_MERGE_3D_ACTIVE,
>>>>    			      BIT(cfg->merge_3d - MERGE_3D_0));
>>>> -	if (cfg->dsc) {
>>>> -		DPU_REG_WRITE(&ctx->hw, CTL_FLUSH, DSC_IDX);
>>>> -		DPU_REG_WRITE(c, CTL_DSC_ACTIVE, cfg->dsc);
>>>> -	}
>>>> +
>>>> +	/* FIXME: fix reset_intf_cfg to handle teardown of dsc */
>>>
>>> There's more wrong than just moving (not "fix"ing) this bit of code into
>>> reset_intf_cfg.  And this will have to be re-wrapped in `if (cfg->dsc)`
>>> again by reverting this patch.  Perhaps that can be explained, or link
>>> to Abhinav's explanation to make it clear to readers what this FIXME
>>> actually means?  Let's wait for Abhinav and Dmitry to confirm the
>>> desired communication here.
>>>
>>> https://lore.kernel.org/linux-arm-msm/ec045d6b-4ffd-0f8c-4011-8db45edc6978@quicinc.com/
>>>
>>
>> Yes, I am fine with linking this explanation in the commit text and
>> mentioning that till thats fixed, we need to go with this solution. The
>> FIXME itself is fine, I will work on it and I remember this context well.
> 
> Looks like it was removed entirely in v3, in favour of only describing
> it in the patch body.  The wording seems a bit off but that's fine by me
> if you're picking this up soon anyway.
> 
> - Marijn