Hi Johan,
On Mon, 31 Mar 2025 at 09:50, Johan Hovold <jo...@kernel.org> wrote:
>
> On Thu, Mar 27, 2025 at 04:56:53PM +0000, Christopher Obbard wrote:
> > The eDP panel has an HPD GPIO. Describe it in the device tree
> > for the generic T14s model, as the HPD GPIO property is used in
> > both the OLED and LCD models which inherit this device tree.
>
> AFAICT, this patch is not correct as the hotplug detect signal is
> connected directly to the display controller on (these) Qualcomm SoCs
> and is already handled by its driver.
>
> Describing it as you do here leads to less accurate delays, see commits:
>
> 2327b13d6c47 ("drm/panel-edp: Take advantage of wait_hpd_asserted()
> in struct drm_dp_aux").
> 3b5765df375c ("drm/panel: atna33xc20: Take advantage of
> wait_hpd_asserted() in struct drm_dp_aux")
>
> Perhaps you lose some other functionality too.
>
> > Reviewed-by: Bryan O'Donoghue <bryan.odonog...@linaro.org>
> > Signed-off-by: Christopher Obbard <christopher.obb...@linaro.org>
> > ---
> > arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi | 11
> > +++++++++++
> > 1 file changed, 11 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi
> > b/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi
> > index
> > 962fb050c55c4fd33f480a21a8c47a484d0c82b8..46c73f5c039ed982b553636cf8c4237a20ba7687
> > 100644
> > --- a/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi
> > @@ -980,8 +980,12 @@ &mdss_dp3 {
> > aux-bus {
> > panel: panel {
> > compatible = "edp-panel";
> > + hpd-gpios = <&tlmm 119 GPIO_ACTIVE_HIGH>;
> > power-supply = <&vreg_edp_3p3>;
> >
> > + pinctrl-0 = <&edp_hpd_n_default>;
> > + pinctrl-names = "default";
> > +
> > port {
> > edp_panel_in: endpoint {
> > remote-endpoint = <&mdss_dp3_out>;
> > @@ -1286,6 +1290,13 @@ hall_int_n_default: hall-int-n-state {
> > bias-disable;
> > };
> >
> > + edp_hpd_n_default: edp-hpd-n-state {
> > + pins = "gpio119";
> > + function = "gpio";
> > + drive-strength = <2>;
> > + bias-pull-up;
> > + };
>
> I checked the firmware configuration for this pin on my T14s, which
> does not match what you have here. Instead the function is set to
> "edp0_hot" which forwards the signal to the display controller which
> already handles the signal on panel power on. (And there is also no
> internal pull up enabled).
>
> We may want to describe this pin configuration somewhere, but that's a
> separate issue.
Thanks for your review, I will send another version in coming days and
drop this first patch (adding hpd to the T14s DTSI).
As a consequence I will need to add no-hpd property to the panel node.
I will add a short comment about how the hpd signal is handled by the
driver already.
Thanks!
Chris
