clk: Skip clamping when rounding if there's no boundaries

Commit 948fb09 ("clk: Always clamp the rounded rate") recently
started to clamp the request rate in the clk_rate_request passed as an
argument of clk_core_determine_round_nolock() with the min_rate and
max_rate fields of that same request.

While the clk_rate_requests created by the framework itself always have
those fields set, some drivers will create it themselves and don't
always fill min_rate and max_rate.

In such a case, we end up clamping the rate with a minimum and maximum
of 0, thus always rounding the rate to 0.

Let's skip the clamping if both min_rate and max_rate are set to 0 and
complain so that it gets fixed.

Fixes: 948fb09 ("clk: Always clamp the rounded rate")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220816112530.1837489-4-maxime@cerno.tech
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Author: mripard

drivers/clk/clk.c

@@ -1341,7 +1341,19 @@ static int clk_core_determine_round_nolock(struct clk_core *core,
 	if (!core)
 		return 0;
 
-	req->rate = clamp(req->rate, req->min_rate, req->max_rate);
+	/*
+	 * Some clock providers hand-craft their clk_rate_requests and
+	 * might not fill min_rate and max_rate.
+	 *
+	 * If it's the case, clamping the rate is equivalent to setting
+	 * the rate to 0 which is bad. Skip the clamping but complain so
+	 * that it gets fixed, hopefully.
+	 */
+	if (!req->min_rate && !req->max_rate)
+		pr_warn("%s: %s: clk_rate_request has initialized min or max rate.\n",
+			__func__, core->name);
+	else
+		req->rate = clamp(req->rate, req->min_rate, req->max_rate);
 
 	/*
 	 * At this point, core protection will be disabled