lkml.org 
[lkml]   [2024]   [Apr]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    SubjectRe: [PATCH] arm64: dts: mediatek: mt8192-asurada: Add off-on-delay-us for pp3300_mipibrdg
    From
    Il 30/04/24 11:32, Pin-yen Lin ha scritto:
    > Hi Angelo,
    >
    > On Tue, Apr 30, 2024 at 4:17 PM AngeloGioacchino Del Regno
    > <angelogioacchino.delregno@collabora.com> wrote:
    >>
    >> Il 29/04/24 11:53, Pin-yen Lin ha scritto:
    >>> Set off-on-delay-us to 500000 us for pp3300_mipibrdg to make sure it
    >>> complies with the panel sequence. Explicit configuration on the
    >>> regulator node is required because mt8192-asurada uses the same power
    >>> supply for the panel and the anx7625 DP bridge. So powering on/off the
    >>> DP bridge could break the power sequence requirement for the panel.
    >>>
    >>> Fixes: f9f00b1f6b9b ("arm64: dts: mediatek: asurada: Add display regulators")
    >>> Signed-off-by: Pin-yen Lin <treapking@chromium.org>
    >>>
    >>
    >> Uhm, there might be more to it - I don't think that this should ever happen.
    >>
    >> The regulator is refcounted, so...
    >> * Bridge on: panel goes off, but regulator doesn't turn off (refcount=1)
    >> * Panel resume -> sequence respected (refcount=2 -> wait -> more vregs, etc)
    >> * Bridge off: panel is already off (refcount=0)
    >> * Bridge resume -> refcount=1, no panel commands yet
    >
    > The off-on-delay could be violated because the bridge driver does not
    > check the delay.
    >
    >> * Panel resume -> refcount=2, wait -> more vregs, etc
    >>
    >> Can you please describe the issue that you're getting?
    >
    > The symptom we observed is that the device has a small chance to
    > reboot to a black panel, and we think the panel's unprepare delay (the
    > time to power down completely) might not be satisfied because the
    > bridge doesn't check that when it enables the regulator. Even if the
    > regulator is enabled by the panel driver, the delay can also be
    > violated in the following sequence:
    >
    > * t=0ms, bridge on: panel goes off, but regulator doesn't turn off
    > (refcount=1). The .unprepared_time in panel_edp is updated
    > * t=300ms, bridge off, regulator goes off (refcount=0)
    > * t=600ms, panel on, the panel driver thinks the unprepare delay
    > (500ms) is satisfied, but the regulator was disabled 300ms ago.
    >
    > Did I miss anything here? Or should I add more detail to the commit message?
    >

    Heh, no you didn't miss anything, this time it's just me :-)

    If you can please add that description to the commit message for a v2 that'd be
    appreciated on my side.

    In any case

    Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

    >>
    >> Cheers,
    >> Angelo
    >>
    > Regards,
    > Pin-yen
    >
    >>> ---
    >>>
    >>> arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi | 1 +
    >>> 1 file changed, 1 insertion(+)
    >>>
    >>> diff --git a/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi b/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi
    >>> index 7a704246678f..08d71ddf3668 100644
    >>> --- a/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi
    >>> +++ b/arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi
    >>> @@ -147,6 +147,7 @@ pp3300_mipibrdg: regulator-3v3-mipibrdg {
    >>> regulator-boot-on;
    >>> gpio = <&pio 127 GPIO_ACTIVE_HIGH>;
    >>> vin-supply = <&pp3300_g>;
    >>> + off-on-delay-us = <500000>;
    >>> };
    >>>
    >>> /* separately switched 3.3V power rail */
    >>


    \
     
     \ /
      Last update: 2024-05-27 18:09    [W:4.583 / U:0.020 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site