drm/i915/power: use intel_de_wait_for_clear() instead of wait_for()

Prefer the register read specific wait function over i915 wait_for_us().

The existing condition is quite complicated. Simplify by checking for
requesters first, and determine timeout based on that. Refresh
requesters in case of timeouts, should one have popped up during the
wait. The downside is that this does not cut the wait short if
requesters show up *during* the wait, but we're talking about 1 ms so
shouldn't be an issue.

v2: Refresh requesters only if there were none before (Imre)

Cc: Imre Deak <[email protected]>
Reviewed-by: Imre Deak <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jani Nikula <[email protected]>

Author: jnikula

drivers/gpu/drm/i915/display/intel_display_power_well.c

@@ -320,8 +320,8 @@ static void hsw_wait_for_power_well_disable(struct intel_display *display,
 {
 	const struct i915_power_well_regs *regs = power_well->desc->ops->regs;
 	int pw_idx = i915_power_well_instance(power_well)->hsw.idx;
-	bool disabled;
 	u32 reqs;
+	int ret;
 
 	/*
 	 * Bspec doesn't require waiting for PWs to get disabled, but still do
@@ -332,12 +332,18 @@ static void hsw_wait_for_power_well_disable(struct intel_display *display,
 	 * Skip the wait in case any of the request bits are set and print a
 	 * diagnostic message.
 	 */
-	wait_for((disabled = !(intel_de_read(display, regs->driver) &
-			       HSW_PWR_WELL_CTL_STATE(pw_idx))) ||
-		 (reqs = hsw_power_well_requesters(display, regs, pw_idx)), 1);
-	if (disabled)
+	reqs = hsw_power_well_requesters(display, regs, pw_idx);
+
+	ret = intel_de_wait_for_clear(display, regs->driver,
+				      HSW_PWR_WELL_CTL_STATE(pw_idx),
+				      reqs ? 0 : 1);
+	if (!ret)
 		return;
 
+	/* Refresh requesters in case they popped up during the wait. */
+	if (!reqs)
+		reqs = hsw_power_well_requesters(display, regs, pw_idx);
+
 	drm_dbg_kms(display->drm,
 		    "%s forced on (bios:%d driver:%d kvmr:%d debug:%d)\n",
 		    intel_power_well_name(power_well),