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Message-ID: <d52b384f-9853-3921-d4f2-5aedb7ef4c61@linaro.org>
Date:   Tue, 30 May 2023 01:39:10 +0300
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Subject: Re: [PATCH RFC 03/10] drm/panel: Add LGD panel driver for Sony Xperia
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To:     Marijn Suijten <marijn.suijten@somainline.org>
Cc:     neil.armstrong@linaro.org, Sam Ravnborg <sam@ravnborg.org>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Caleb Connolly <caleb@connolly.tech>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <andersson@kernel.org>,
        ~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>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        Abhinav Kumar <quic_abhinavk@quicinc.com>,
        Kuogee Hsieh <quic_khsieh@quicinc.com>,
        Jessica Zhang <quic_jesszhan@quicinc.com>
References: <20230521-drm-panels-sony-v1-0-541c341d6bee@somainline.org>
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 <ccc97880-8e74-b85b-9679-9c12c44c4b99@linaro.org>
 <71675a02-0801-62dc-2673-4a0907636b21@linaro.org>
 <CAA8EJpq=HZqiBZ6bpUNH47VmASuH+Mi5OD5BHmg0TPwtsKHf8w@mail.gmail.com>
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 <ebc3ff33-6e4f-b107-33c6-f35b03307058@linaro.org>
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From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
In-Reply-To: <v3ac2ihqjce7vxcsjnm7ett2vc6wb4hb3bb6x4widd55eintw7@fgkyipbbl2ei>
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On 30/05/2023 01:37, Marijn Suijten wrote:
> On 2023-05-30 01:18:40, Dmitry Baryshkov wrote:
> <snip>
>>>>>>> +    ret = mipi_dsi_dcs_set_display_on(dsi);
>>>>>>> +    if (ret < 0) {
>>>>>>> +        dev_err(dev, "Failed to turn display on: %d\n", ret);
>>>>>>> +        return ret;
>>>>>>> +    }
>>>>>>
>>>>>> My usual question: should the mipi_dsi_dcs_exit_sleep_mode() / mipi_dsi_dcs_set_display_on() be moved from prepare() to enable() part?
>>>>>
>>>>>
>>>>> No, prepare is called before the video stream is started and when display is still in LPM mode and the mode hasn't been set.
>>>>>
>>>>
>>>> Yes, that's my point. Shouldn't we enable the panel _after_ starting the stream?
>>>
>>> I have never investigated what it takes to split these functions, but
>>> some of these panels do show some corruption at startup which may be
>>> circumvented by powering the panel on after starting the video stream?
>>>
>>> I'm just not sure where to make the split: downstream does describe a
>>> qcom,mdss-dsi-on-command and qcom,mdss-dsi-post-panel-on-command, where
>>> the latter only contains set_display_on() (not exit_sleep_mode()).
>>> It is documented like:
>>>
>>>       same as "qcom,mdss-dsi-on-command" except commands are sent after
>>>       displaying an image."
>>>
>>> So this seems like the right way to split them up, I'll test this out on
>>> all submitted panel drivers.
>>
>> Interesting enough, Neil suggested that sending all the commands during
>> pre_enable() is the correct sequence (especially for VIDEO mode panels),
>> since not all DSI hosts can send commands after switching to the VIDEO mode.
> 
> Note that all these panels and Driver-ICs are command-mode, and/or
> programmed to run in command-mode, so there shouldn't be any notion of a
> VIDEO stream (any command-mode frame is just an "arbitrary command" as
> far as I understood).

Yes, from the data stream point of view. I was talking about the DSI 
host being able to send arbitrary commands or not after enabling the 
video/cmd stream.

> 
> - Marijn

-- 
With best wishes
Dmitry