Re: [PATCH v4 16/27] drm/panel: panel-simple: Get rid of hacky HPD chicken-and-egg code

Bjorn Andersson
2021-04-23T14:50:55Z

On Fri 16 Apr 17:39 CDT 2021, Douglas Anderson wrote:

> 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.
>

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>

Regards,
Bjorn

> 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
>