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From: Maxime Ripard <maxime@cerno.tech>
To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	Maxime Ripard <maxime@cerno.tech>,
	Daniel Vetter <daniel.vetter@intel.com>,
	David Airlie <airlied@linux.ie>
Cc: linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org,
	linux-rpi-kernel@lists.infradead.org,
	Mike Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>,
	Nicolas Saenz Julienne <nsaenz@kernel.org>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Michael Stapelberg <michael@stapelberg.ch>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH 3/5] drm/vc4: hdmi: Set a default HSM rate
Date: Wed, 22 Sep 2021 14:54:17 +0200	[thread overview]
Message-ID: <20210922125419.4125779-4-maxime@cerno.tech> (raw)
In-Reply-To: <20210922125419.4125779-1-maxime@cerno.tech>

When the firmware doesn't setup the HSM rate (such as when booting
without an HDMI cable plugged in), its rate is 0 and thus any register
access results in a CPU stall, even though HSM is enabled.

Let's enforce a minimum rate at boot to avoid this issue.

Fixes: 4f6e3d66ac52 ("drm/vc4: Add runtime PM support to the HDMI encoder driver")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index b4b4653fe301..74222b12f8c8 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -94,6 +94,7 @@
 # define VC4_HD_M_SW_RST			BIT(2)
 # define VC4_HD_M_ENABLE			BIT(0)
 
+#define HSM_MIN_CLOCK_FREQ	120000000
 #define CEC_CLOCK_FREQ 40000
 
 #define HDMI_14_MAX_TMDS_CLK   (340 * 1000 * 1000)
@@ -2169,6 +2170,19 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data)
 			vc4_hdmi->disable_4kp60 = true;
 	}
 
+	/*
+	 * If we boot without any cable connected to the HDMI connector,
+	 * the firmware will skip the HSM initialization and leave it
+	 * with a rate of 0, resulting in a bus lockup when we're
+	 * accessing the registers even if it's enabled.
+	 *
+	 * Let's put a sensible default at runtime_resume so that we
+	 * don't end up in this situation.
+	 */
+	ret = clk_set_min_rate(vc4_hdmi->hsm_clock, HSM_MIN_CLOCK_FREQ);
+	if (ret)
+		goto err_put_ddc;
+
 	if (vc4_hdmi->variant->reset)
 		vc4_hdmi->variant->reset(vc4_hdmi);
 
-- 
2.31.1


WARNING: multiple messages have this Message-ID (diff)
From: Maxime Ripard <maxime@cerno.tech>
To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	Maxime Ripard <maxime@cerno.tech>,
	Daniel Vetter <daniel.vetter@intel.com>,
	David Airlie <airlied@linux.ie>
Cc: linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org,
	linux-rpi-kernel@lists.infradead.org,
	Mike Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>,
	Nicolas Saenz Julienne <nsaenz@kernel.org>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Michael Stapelberg <michael@stapelberg.ch>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH 3/5] drm/vc4: hdmi: Set a default HSM rate
Date: Wed, 22 Sep 2021 14:54:17 +0200	[thread overview]
Message-ID: <20210922125419.4125779-4-maxime@cerno.tech> (raw)
In-Reply-To: <20210922125419.4125779-1-maxime@cerno.tech>

When the firmware doesn't setup the HSM rate (such as when booting
without an HDMI cable plugged in), its rate is 0 and thus any register
access results in a CPU stall, even though HSM is enabled.

Let's enforce a minimum rate at boot to avoid this issue.

Fixes: 4f6e3d66ac52 ("drm/vc4: Add runtime PM support to the HDMI encoder driver")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index b4b4653fe301..74222b12f8c8 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -94,6 +94,7 @@
 # define VC4_HD_M_SW_RST			BIT(2)
 # define VC4_HD_M_ENABLE			BIT(0)
 
+#define HSM_MIN_CLOCK_FREQ	120000000
 #define CEC_CLOCK_FREQ 40000
 
 #define HDMI_14_MAX_TMDS_CLK   (340 * 1000 * 1000)
@@ -2169,6 +2170,19 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data)
 			vc4_hdmi->disable_4kp60 = true;
 	}
 
+	/*
+	 * If we boot without any cable connected to the HDMI connector,
+	 * the firmware will skip the HSM initialization and leave it
+	 * with a rate of 0, resulting in a bus lockup when we're
+	 * accessing the registers even if it's enabled.
+	 *
+	 * Let's put a sensible default at runtime_resume so that we
+	 * don't end up in this situation.
+	 */
+	ret = clk_set_min_rate(vc4_hdmi->hsm_clock, HSM_MIN_CLOCK_FREQ);
+	if (ret)
+		goto err_put_ddc;
+
 	if (vc4_hdmi->variant->reset)
 		vc4_hdmi->variant->reset(vc4_hdmi);
 
-- 
2.31.1


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  parent reply	other threads:[~2021-09-22 12:54 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-22 12:54 [PATCH 0/5] drm/vc4: hdmi: Remove CPU hangs, take 2 Maxime Ripard
2021-09-22 12:54 ` Maxime Ripard
2021-09-22 12:54 ` [PATCH 1/5] clk: bcm-2835: Pick the closest clock rate Maxime Ripard
2021-09-22 12:54   ` Maxime Ripard
2021-09-28 16:26   ` nicolas saenz julienne
2021-09-28 16:26     ` nicolas saenz julienne
2021-09-30 18:08   ` Stephen Boyd
2021-09-30 18:08     ` Stephen Boyd
2021-10-13 12:59   ` (subset) " Maxime Ripard
2021-10-13 12:59     ` Maxime Ripard
2021-09-22 12:54 ` [PATCH 2/5] clk: bcm-2835: Remove rounding up the dividers Maxime Ripard
2021-09-22 12:54   ` Maxime Ripard
2021-09-28 16:26   ` nicolas saenz julienne
2021-09-28 16:26     ` nicolas saenz julienne
2021-09-29 13:27     ` Maxime Ripard
2021-09-29 13:27       ` Maxime Ripard
2021-09-30 18:09   ` Stephen Boyd
2021-09-30 18:09     ` Stephen Boyd
2021-10-13 12:59   ` (subset) " Maxime Ripard
2021-10-13 12:59     ` Maxime Ripard
2021-09-22 12:54 ` Maxime Ripard [this message]
2021-09-22 12:54   ` [PATCH 3/5] drm/vc4: hdmi: Set a default HSM rate Maxime Ripard
2021-09-30 15:51   ` nicolas saenz julienne
2021-09-30 15:51     ` nicolas saenz julienne
2021-10-13 12:59   ` (subset) " Maxime Ripard
2021-10-13 12:59     ` Maxime Ripard
2021-09-22 12:54 ` [PATCH 4/5] drm/vc4: hdmi: Move the HSM clock enable to runtime_pm Maxime Ripard
2021-09-22 12:54   ` Maxime Ripard
2021-09-30 15:54   ` nicolas saenz julienne
2021-09-30 15:54     ` nicolas saenz julienne
2021-10-13 12:59   ` (subset) " Maxime Ripard
2021-10-13 12:59     ` Maxime Ripard
2021-09-22 12:54 ` [PATCH 5/5] drm/vc4: hdmi: Make sure the controller is powered in detect Maxime Ripard
2021-09-22 12:54   ` Maxime Ripard
2021-09-30 15:55   ` nicolas saenz julienne
2021-09-30 15:55     ` nicolas saenz julienne
2021-10-13 12:59   ` (subset) " Maxime Ripard
2021-10-13 12:59     ` Maxime Ripard
     [not found] ` <CANnVG6kFC7q_dDDp4rRZsJz=paHKy2STn9127LE=JJOf2kW2TA@mail.gmail.com>
2021-09-23  7:05   ` [PATCH 0/5] drm/vc4: hdmi: Remove CPU hangs, take 2 Michael Stapelberg
2021-09-23  7:05     ` Michael Stapelberg
2021-09-24  7:40 ` Maxime Ripard
2021-09-24  7:40   ` Maxime Ripard
2021-09-28 13:05   ` Maxime Ripard
2021-09-28 13:05     ` Maxime Ripard
2021-09-30 18:09     ` Stephen Boyd
2021-09-30 18:09       ` Stephen Boyd
2021-09-30 18:39       ` Florian Fainelli
2021-09-30 18:39         ` Florian Fainelli

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