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    Subject[PATCH v4 16/27] drm/panel: panel-simple: Get rid of hacky HPD chicken-and-egg code
    Date
    When I added support for the hpd-gpio to simple-panel in commit
    48834e6084f1 ("drm/panel-simple: Support hpd-gpios for delaying
    prepare()"), I added a special case to handle a circular dependency I
    was running into on the ti-sn65dsi86 bridge chip. On my board the
    hpd-gpio is actually provided by the bridge chip. That was causing
    some circular dependency problems that I had to work around by getting
    the hpd-gpio late.

    I've now reorganized the ti-sn65dsi86 bridge chip driver to be a
    collection of sub-drivers. Now the GPIO part can probe separately and
    that breaks the chain. Let's get rid of the old code to clean things
    up.

    Signed-off-by: Douglas Anderson <dianders@chromium.org>
    ---

    (no changes since v1)

    drivers/gpu/drm/panel/panel-simple.c | 24 +++++-------------------
    1 file changed, 5 insertions(+), 19 deletions(-)

    diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
    index 6b22872b3281..90a17ca79d06 100644
    --- a/drivers/gpu/drm/panel/panel-simple.c
    +++ b/drivers/gpu/drm/panel/panel-simple.c
    @@ -366,8 +366,7 @@ static int panel_simple_unprepare(struct drm_panel *panel)
    return 0;
    }

    -static int panel_simple_get_hpd_gpio(struct device *dev,
    - struct panel_simple *p, bool from_probe)
    +static int panel_simple_get_hpd_gpio(struct device *dev, struct panel_simple *p)
    {
    int err;

    @@ -375,17 +374,10 @@ static int panel_simple_get_hpd_gpio(struct device *dev,
    if (IS_ERR(p->hpd_gpio)) {
    err = PTR_ERR(p->hpd_gpio);

    - /*
    - * If we're called from probe we won't consider '-EPROBE_DEFER'
    - * to be an error--we'll leave the error code in "hpd_gpio".
    - * When we try to use it we'll try again. This allows for
    - * circular dependencies where the component providing the
    - * hpd gpio needs the panel to init before probing.
    - */
    - if (err != -EPROBE_DEFER || !from_probe) {
    + if (err != -EPROBE_DEFER)
    dev_err(dev, "failed to get 'hpd' GPIO: %d\n", err);
    - return err;
    - }
    +
    + return err;
    }

    return 0;
    @@ -416,12 +408,6 @@ static int panel_simple_prepare_once(struct panel_simple *p)
    msleep(delay);

    if (p->hpd_gpio) {
    - if (IS_ERR(p->hpd_gpio)) {
    - err = panel_simple_get_hpd_gpio(dev, p, false);
    - if (err)
    - goto error;
    - }
    -
    if (p->desc->delay.hpd_absent_delay)
    hpd_wait_us = p->desc->delay.hpd_absent_delay * 1000UL;
    else
    @@ -682,7 +668,7 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)

    panel->no_hpd = of_property_read_bool(dev->of_node, "no-hpd");
    if (!panel->no_hpd) {
    - err = panel_simple_get_hpd_gpio(dev, panel, true);
    + err = panel_simple_get_hpd_gpio(dev, panel);
    if (err)
    return err;
    }
    --
    2.31.1.368.gbe11c130af-goog
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