Messages in this thread | | | Date | Thu, 2 Jun 2022 13:22:35 +0300 | Subject | Re: [PATCH v3 1/4] drm/dp: Add wait_hpd_asserted() callback to struct drm_dp_aux | From | Dmitry Baryshkov <> |
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On 18/04/2022 20:17, Douglas Anderson wrote: > Sometimes it's useful for users of the DP AUX bus (like panels) to be > able to poll HPD. Let's add a callback that allows DP AUX busses > drivers to provide this. > > Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> > Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> --- > Left Dmitry's Reviewed-by tag off since patch changed enough. > > (no changes since v2) > > Changes in v2: > - Change is_hpd_asserted() to wait_hpd_asserted() > > include/drm/dp/drm_dp_helper.h | 26 ++++++++++++++++++++++++++ > 1 file changed, 26 insertions(+) > > diff --git a/include/drm/dp/drm_dp_helper.h b/include/drm/dp/drm_dp_helper.h > index 53d1e722f4de..0940c415db8c 100644 > --- a/include/drm/dp/drm_dp_helper.h > +++ b/include/drm/dp/drm_dp_helper.h > @@ -2035,6 +2035,32 @@ struct drm_dp_aux { > ssize_t (*transfer)(struct drm_dp_aux *aux, > struct drm_dp_aux_msg *msg); > > + /** > + * @wait_hpd_asserted: wait for HPD to be asserted > + * > + * This is mainly useful for eDP panels drivers to wait for an eDP > + * panel to finish powering on. This is an optional function. > + * > + * This function will efficiently wait for up to `wait_us` microseconds > + * for HPD to be asserted and might sleep. > + * > + * This function returns 0 if HPD was asserted or -ETIMEDOUT if time > + * expired and HPD wasn't asserted. This function should not print > + * timeout errors to the log. > + * > + * The semantics of this function are designed to match the > + * readx_poll_timeout() function. That means a `wait_us` of 0 means > + * to wait forever. If you want to do a quick poll you could pass 1 > + * for `wait_us`. > + * > + * NOTE: this function specifically reports the state of the HPD pin > + * that's associated with the DP AUX channel. This is different from > + * the HPD concept in much of the rest of DRM which is more about > + * physical presence of a display. For eDP, for instance, a display is > + * assumed always present even if the HPD pin is deasserted. > + */ > + int (*wait_hpd_asserted)(struct drm_dp_aux *aux, unsigned long wait_us); > + > /** > * @i2c_nack_count: Counts I2C NACKs, used for DP validation. > */
-- With best wishes Dmitry
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