Hi,
On Thu, Jun 2, 2022 at 8:12 AM Dmitry Baryshkov
<dmitry.barysh...@linaro.org> wrote:
>
> On 18/04/2022 20:17, Douglas Anderson wrote:
> > Let's add support for being able to read the HPD pin even if it's
> > hooked directly to the controller. This will allow us to get more
> > accurate delays also lets us take away the waiting in the AUX transfer
> > functions of the eDP controller drivers.
> >
> > Signed-off-by: Douglas Anderson <diand...@chromium.org>
>
> Reviewed-by: Dmitry Baryshkov <dmitry.barysh...@linaro.org>
>
> > ---
> >
> > (no changes since v2)
> >
> > Changes in v2:
> > - Change is_hpd_asserted() to wait_hpd_asserted()
> >
> > drivers/gpu/drm/panel/panel-edp.c | 33 +++++++++++++++++++++----------
> > 1 file changed, 23 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/panel/panel-edp.c
> > b/drivers/gpu/drm/panel/panel-edp.c
> > index 1732b4f56e38..086e0bf52fb9 100644
> > --- a/drivers/gpu/drm/panel/panel-edp.c
> > +++ b/drivers/gpu/drm/panel/panel-edp.c
> > @@ -417,6 +417,11 @@ static int panel_edp_get_hpd_gpio(struct device *dev,
> > struct panel_edp *p)
> > return 0;
> > }
> >
> > +static bool panel_edp_can_read_hpd(struct panel_edp *p)
> > +{
> > + return !p->no_hpd && (p->hpd_gpio || (p->aux &&
> > p->aux->wait_hpd_asserted));
> > +}
> > +
> > static int panel_edp_prepare_once(struct panel_edp *p)
> > {
> > struct device *dev = p->base.dev;
> > @@ -441,17 +446,21 @@ static int panel_edp_prepare_once(struct panel_edp *p)
> > if (delay)
> > msleep(delay);
> >
> > - if (p->hpd_gpio) {
> > + if (panel_edp_can_read_hpd(p)) {
> > if (p->desc->delay.hpd_absent)
> > hpd_wait_us = p->desc->delay.hpd_absent * 1000UL;
> > else
> > hpd_wait_us = 2000000;
> >
> > - err = readx_poll_timeout(gpiod_get_value_cansleep,
> > p->hpd_gpio,
> > - hpd_asserted, hpd_asserted,
> > - 1000, hpd_wait_us);
> > - if (hpd_asserted < 0)
> > - err = hpd_asserted;
> > + if (p->hpd_gpio) {
> > + err = readx_poll_timeout(gpiod_get_value_cansleep,
> > + p->hpd_gpio, hpd_asserted,
> > + hpd_asserted, 1000,
> > hpd_wait_us);
> > + if (hpd_asserted < 0)
> > + err = hpd_asserted;
> > + } else {
> > + err = p->aux->wait_hpd_asserted(p->aux, hpd_wait_us);
> > + }
>
> I'm close to thinking that this construct deserves a separate helper.
Just to close the loop: I didn't try to create a helper for v5. I'm
not completely convinced that this will be common. I would tend to
expect that having HPD handled by a GPIO is somewhat rare. It's also
fairly rare to have a panel that's not handled by the generic
panel-edp. We ended up with the GPIO on trogdor because of the weird
debouncing on sn85dsi86 and we ended up with one case of not using
edp-panel on trogdor because of the weird power sequencing of the
Samsung OLED panel that's on homestar.
I'd also note that the generic eDP panel has a special case for
"timeout" which we don't have on the Samsung panel to handle at least
one panel I found that sometimes simply didn't come up but then
_would_ come up on a retry...
That doesn't mean we couldn't abstract it out later, of course. ;-)
-Doug
-Doug
