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    SubjectRe: [PATCH] drm/bridge: ps8640: Add double reset T4 and T5 to power-on sequence
    Hsin-Yi Wang <hsinyi@chromium.org> 於 2022年8月15日 週一 下午5:39寫道:
    >
    > The double reset power-on sequence is a workaround for the hardware
    > flaw in some chip that SPI Clock output glitch and cause internal MPU
    > unable to read firmware correctly. The sequence is suggested in ps8640
    > application note.
    >
    > Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>

    Reviewed-by: Rock Chiu <rock.chiu@paradetech.corp-partner.google.com>
    >
    > ---
    >
    > drivers/gpu/drm/bridge/parade-ps8640.c | 5 +++++
    > 1 file changed, 5 insertions(+)
    >
    > diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
    > index 49107a6cdac18..d7483c13c569b 100644
    > --- a/drivers/gpu/drm/bridge/parade-ps8640.c
    > +++ b/drivers/gpu/drm/bridge/parade-ps8640.c
    > @@ -375,6 +375,11 @@ static int __maybe_unused ps8640_resume(struct device *dev)
    > gpiod_set_value(ps_bridge->gpio_reset, 1);
    > usleep_range(2000, 2500);
    > gpiod_set_value(ps_bridge->gpio_reset, 0);
    > + /* Double reset for T4 and T5 */
    > + msleep(50);
    > + gpiod_set_value(ps_bridge->gpio_reset, 1);
    > + msleep(50);
    > + gpiod_set_value(ps_bridge->gpio_reset, 0);
    >
    > /*
    > * Mystery 200 ms delay for the "MCU to be ready". It's unclear if
    > --
    > 2.37.1.595.g718a3a8f04-goog
    >

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