linux-kernel - [PATCH 1/2] drm/vc4: hdmi: Check the device state in prepare()

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Message-Id: <20210924135530.1036564-2-maxime@cerno.tech>
Date:   Fri, 24 Sep 2021 15:55:29 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Maxime Ripard <maxime@...no.tech>
Cc:     Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>
Subject: [PATCH 1/2] drm/vc4: hdmi: Check the device state in prepare()

Even though we already check that the encoder->crtc pointer is there
during in startup(), which is part of the open() path in ASoC, nothing
guarantees that our encoder state won't change between the time when we
open the device and the time we prepare it.

Move the sanity checks we do in startup() to a helper and call it from
prepare().

Fixes: 91e99e113929 ("drm/vc4: hdmi: Register HDMI codec")
Signed-off-by: Maxime Ripard <maxime@...no.tech>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index b4b4653fe301..74f9df38815e 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -1227,17 +1227,31 @@ static inline struct vc4_hdmi *dai_to_hdmi(struct snd_soc_dai *dai)
 	return snd_soc_card_get_drvdata(card);
 }
 
+static bool vc4_hdmi_audio_can_stream(struct vc4_hdmi *vc4_hdmi)
+{
+	struct drm_encoder *encoder = &vc4_hdmi->encoder.base.base;
+
+	/*
+	 * The encoder doesn't have a CRTC until the first modeset.
+	 */
+	if (!encoder->crtc)
+		return false;
+
+	/*
+	 * If the encoder is currently in DVI mode, treat the codec DAI
+	 * as missing.
+	 */
+	if (!(HDMI_READ(HDMI_RAM_PACKET_CONFIG) & VC4_HDMI_RAM_PACKET_ENABLE))
+		return false;
+
+	return true;
+}
+
 static int vc4_hdmi_audio_startup(struct device *dev, void *data)
 {
 	struct vc4_hdmi *vc4_hdmi = dev_get_drvdata(dev);
-	struct drm_encoder *encoder = &vc4_hdmi->encoder.base.base;
 
-	/*
-	 * If the HDMI encoder hasn't probed, or the encoder is
-	 * currently in DVI mode, treat the codec dai as missing.
-	 */
-	if (!encoder->crtc || !(HDMI_READ(HDMI_RAM_PACKET_CONFIG) &
-				VC4_HDMI_RAM_PACKET_ENABLE))
+	if (!vc4_hdmi_audio_can_stream(vc4_hdmi))
 		return -ENODEV;
 
 	vc4_hdmi->audio.streaming = true;
@@ -1339,6 +1353,9 @@ static int vc4_hdmi_audio_prepare(struct device *dev, void *data,
 	u32 mai_audio_format;
 	u32 mai_sample_rate;
 
+	if (!vc4_hdmi_audio_can_stream(vc4_hdmi))
+		return -EINVAL;
+
 	dev_dbg(dev, "%s: %u Hz, %d bit, %d channels\n", __func__,
 		sample_rate, params->sample_width, channels);
 
-- 
2.31.1