linux-kernel - [PATCH v2 7/7] drm/vc4: Make sure we don't end up with a core clock too high

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Date:   Tue, 20 Sep 2022 14:50:26 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Daniel Vetter <daniel@...ll.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Michael Turquette <mturquette@...libre.com>,
        Scott Branden <sbranden@...adcom.com>,
        Stephen Boyd <sboyd@...nel.org>, Emma Anholt <emma@...olt.net>,
        Ray Jui <rjui@...adcom.com>, Maxime Ripard <mripard@...nel.org>
Cc:     linux-rpi-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, Dom Cobley <popcornmix@...il.com>,
        dri-devel@...ts.freedesktop.org, Maxime Ripard <maxime@...no.tech>,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v2 7/7] drm/vc4: Make sure we don't end up with a core clock too high

Following the clock rate range improvements to the clock framework,
trying to set a disjoint range on a clock will now result in an error.

Thus, we can't set a minimum rate higher than the maximum reported by
the firmware, or clk_set_min_rate() will fail.

Thus we need to clamp the rate we are about to ask for to the maximum
rate possible on that clock.

Signed-off-by: Maxime Ripard <maxime@...no.tech>

diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
index b45dcdfd7306..d241620fd5a7 100644
--- a/drivers/gpu/drm/vc4/vc4_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_kms.c
@@ -397,8 +397,8 @@ static void vc4_atomic_commit_tail(struct drm_atomic_state *state)
 	if (vc4->is_vc5) {
 		unsigned long state_rate = max(old_hvs_state->core_clock_rate,
 					       new_hvs_state->core_clock_rate);
-		unsigned long core_rate = max_t(unsigned long,
-						500000000, state_rate);
+		unsigned long core_rate = clamp_t(unsigned long, state_rate,
+						  500000000, hvs->max_core_rate);
 
 		drm_dbg(dev, "Raising the core clock at %lu Hz\n", core_rate);
 
@@ -432,14 +432,17 @@ static void vc4_atomic_commit_tail(struct drm_atomic_state *state)
 	drm_atomic_helper_cleanup_planes(dev, state);
 
 	if (vc4->is_vc5) {
-		drm_dbg(dev, "Running the core clock at %lu Hz\n",
-			new_hvs_state->core_clock_rate);
+		unsigned long core_rate = min_t(unsigned long,
+						hvs->max_core_rate,
+						new_hvs_state->core_clock_rate);
+
+		drm_dbg(dev, "Running the core clock at %lu Hz\n", core_rate);
 
 		/*
 		 * Request a clock rate based on the current HVS
 		 * requirements.
 		 */
-		WARN_ON(clk_set_min_rate(hvs->core_clk, new_hvs_state->core_clock_rate));
+		WARN_ON(clk_set_min_rate(hvs->core_clk, core_rate));
 
 		drm_dbg(dev, "Core clock actual rate: %lu Hz\n",
 			clk_get_rate(hvs->core_clk));

-- 
b4 0.10.0