linux-kernel - Re: [PATCH v2 1/2] drm/panel: jd9365da: Modify Kingdisplay and Melfas panel timing

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <CA+6=WdTuq4rOakKPwnC82twT1yWG09w6bcpztAXQ3p_vQqrnyg@mail.gmail.com>
Date: Wed, 25 Sep 2024 09:19:54 +0800
From: zhaoxiong lv <lvzhaoxiong@...qin.corp-partner.google.com>
To: Jessica Zhang <quic_jesszhan@...cinc.com>
Cc: neil.armstrong@...aro.org, sam@...nborg.org, 
	maarten.lankhorst@...ux.intel.com, mripard@...nel.org, tzimmermann@...e.de, 
	airlied@...il.com, simona@...ll.ch, dianders@...omium.org, hsinyi@...gle.com, 
	awarnecke002@...mail.com, dmitry.baryshkov@...aro.org, 
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] drm/panel: jd9365da: Modify Kingdisplay and Melfas
 panel timing

On Wed, Sep 25, 2024 at 12:11 AM Jessica Zhang
<quic_jesszhan@...cinc.com> wrote:
>
>
>
> On 9/23/2024 7:13 PM, zhaoxiong lv wrote:
> > On Tue, Sep 24, 2024 at 5:14 AM Jessica Zhang <quic_jesszhan@...cinc.com> wrote:
> >>
> >>
> >>
> >> On 9/23/2024 6:42 AM, Zhaoxiong Lv wrote:
> >>> In MTK chips, if the system starts suspending before the DRM runtime
> >>> resume has not completed, there is a possibility of a black screen
> >>> after waking the machine. Reduce the disable delay resolves this issue,
> >>
> >> Hi Zhaoxiong,
> >>
> >> Do you mean "if the system starts suspending before the DRM runtime
> >> resume *has* completed" here?
> >
> > Hi Jessica
> >
> > Sorry, my description may not be clear enough. It should be when the
> > DRM runtime resume has not yet completed and the system enters sleep
> > mode at the same time.
>
> Got it, yes I think the reworded explanation in your reply is much clearer.
>
> >
> >
> >>
> >>>
> >>> The "backlight_off_to_display_off_delay_ms" was added between
> >>> "backlight off" and "display off"  to prevent "display off" from being
> >>> executed when the backlight is not fully powered off, which may cause
> >>> a white screen. However, we removed this
> >>> "backlight_off_to_display_off_delay_ms" and found that this situation
> >>> did not occur. Therefore, in order to solve the problem mentioned
> >>> above, we We reduced it from 100ms to 3ms (tCMD_OFF >= 1ms).
> >>
> >> So from my understanding of this paragraph,
> >> `backlight_off_to_display_off_delay_ms` was added to prevent the display
> >> powering off before backlight is fully powered off. You recently tested
> >> dropping this completely and saw no issue with this.
> >>
> >> If that's the case, why not drop this delay completely?
> >>
> >> Thanks,
> >>
> >> Jessica Zhang
> >
> > Yes, there are currently no other issue after removing this delay.
> > The reason why I didn't completely remove this delay is because the
> > panel spec states that a delay of more than 1ms  (tCMD_OFF >= 1ms) is
> > required when entering diaplay_off (0x28H), so I reserved 3ms.
>
> Thanks for the clarification -- I see why you included the "(tCMD_OFF >=
> 1ms)" part now. Can you please specify in the commit message that the
> tCMD_OFF delay requirement is from the spec?
>
> Also can you remove the extra "We" in "we We reduced it from 100ms to 3ms"?
>
> Thanks,
>
> Jessica Zhang

OK, thanks for your correction, we will modify the commit message in
the next patch.

>
> >
> >>
> >>>
> >>> This is the timing specification for the two panels:
> >>> 1. Kingdisplay panel timing spec:
> >>> https://github.com/KD54183/-JD9365DA_Power-On-Off-Sequence_V0120240923
> >>> 2. LMFBX101117480 timing spec: https://github.com/chiohsin-lo/TDY-JD_LIB
> >>>
> >>>
> >>> Fixes: 2b976ad760dc ("drm/panel: jd9365da: Support for kd101ne3-40ti MIPI-DSI panel")
> >>> Fixes: c4ce398cf18a ("drm/panel: jd9365da: Support for Melfas lmfbx101117480 MIPI-DSI panel")
> >>>
> >>> Signed-off-by: Zhaoxiong Lv <lvzhaoxiong@...qin.corp-partner.google.com>
> >>> ---
> >>> Changes between V2 and V1:
> >>> -  1. Modify the commit message
> >>> -  2. Modify the value of backlight_off_to_display_off_delay_ms.
> >>> v1: https://lore.kernel.org/all/20240915080830.11318-2-lvzhaoxiong@huaqin.corp-partner.google.com/
> >>> ---
> >>>    drivers/gpu/drm/panel/panel-jadard-jd9365da-h3.c | 4 ++--
> >>>    1 file changed, 2 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/gpu/drm/panel/panel-jadard-jd9365da-h3.c b/drivers/gpu/drm/panel/panel-jadard-jd9365da-h3.c
> >>> index 44897e5218a6..486aa20e5518 100644
> >>> --- a/drivers/gpu/drm/panel/panel-jadard-jd9365da-h3.c
> >>> +++ b/drivers/gpu/drm/panel/panel-jadard-jd9365da-h3.c
> >>> @@ -858,7 +858,7 @@ static const struct jadard_panel_desc kingdisplay_kd101ne3_40ti_desc = {
> >>>        .reset_before_power_off_vcioo = true,
> >>>        .vcioo_to_lp11_delay_ms = 5,
> >>>        .lp11_to_reset_delay_ms = 10,
> >>> -     .backlight_off_to_display_off_delay_ms = 100,
> >>> +     .backlight_off_to_display_off_delay_ms = 3,
> >>>        .display_off_to_enter_sleep_delay_ms = 50,
> >>>        .enter_sleep_to_reset_down_delay_ms = 100,
> >>>    };
> >>> @@ -1109,7 +1109,7 @@ static const struct jadard_panel_desc melfas_lmfbx101117480_desc = {
> >>>        .reset_before_power_off_vcioo = true,
> >>>        .vcioo_to_lp11_delay_ms = 5,
> >>>        .lp11_to_reset_delay_ms = 10,
> >>> -     .backlight_off_to_display_off_delay_ms = 100,
> >>> +     .backlight_off_to_display_off_delay_ms = 3,
> >>>        .display_off_to_enter_sleep_delay_ms = 50,
> >>>        .enter_sleep_to_reset_down_delay_ms = 100,
> >>>    };
> >>> --
> >>> 2.17.1
> >>>
> >>
>