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drm/dp: Add wait_hpd_asserted() callback to struct drm_dp_aux

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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>
Link: https://patchwork.freedesktop.org/patch/msgid/20220614145327.v4.1.Icf57bb12233a47727013c6ab69eebf803e22ebc1@changeid
This commit is contained in:
Douglas Anderson 2022-06-14 14:54:15 -07:00
parent 15b9ca1641
commit 841d742f09
1 changed files with 30 additions and 0 deletions
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30
include/drm/display/drm_dp_helper.h
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@ -389,6 +389,36 @@ 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 the HPD signal to be
* asserted. The `wait_us` parameter that is passed in says that we
* know that the HPD signal is expected to be asserted within `wait_us`
* microseconds. This function could wait for longer than `wait_us` if
* the logic in the DP controller has a long debouncing time. The
* important thing is that if this function returns success that the
* DP controller is ready to send AUX transactions.
*
* 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. Like readx_poll_timeout(), this function may sleep.
*
* 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.
*/