From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yakir Yang Subject: Re: [PATCH 10/12] drm: bridge/dw_hdmi: fix phy enable/disable handling Date: Wed, 07 Oct 2015 12:05:37 +0800 Message-ID: <56149A11.4070102@rock-chips.com> References: <20150808160251.GM7557@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0263446083==" Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Russell King , linux-rockchip@lists.infradead.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Fabio Estevam , Andy Yan List-Id: linux-rockchip.vger.kernel.org This is a multi-part message in MIME format. --===============0263446083== Content-Type: multipart/alternative; boundary="------------070200020706080003070904" This is a multi-part message in MIME format. --------------070200020706080003070904 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit On 08/09/2015 12:04 AM, Russell King wrote: > The dw_hdmi enable/disable handling is particularly weak in several > regards: > * The hotplug interrupt could call hdmi_poweron() or hdmi_poweroff() > while DRM is setting a mode, which could race with a mode being set. > * Hotplug will always re-enable the phy whenever it detects an active > hotplug signal, even if DRM has disabled the output. > > Resolve all of these by introducing a mutex to prevent races, and a > state-tracking bool so we know whether DRM wishes the output to be > enabled. We choose to use our own mutex rather than ->struct_mutex > so that we can still process interrupts in a timely fashion. > > Signed-off-by: Russell King > --- > drivers/gpu/drm/bridge/dw_hdmi.c | 29 ++++++++++++++++++++++------- > 1 file changed, 22 insertions(+), 7 deletions(-) > > diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c > index 7b8a4e942a71..0ee188930d26 100644 > --- a/drivers/gpu/drm/bridge/dw_hdmi.c > +++ b/drivers/gpu/drm/bridge/dw_hdmi.c > @@ -125,6 +125,9 @@ struct dw_hdmi { > bool sink_is_hdmi; > bool sink_has_audio; > > + struct mutex mutex; /* for state below and previous_mode */ > + bool disabled; /* DRM has disabled our bridge */ > + > spinlock_t audio_lock; > struct mutex audio_mutex; > unsigned int sample_rate; > @@ -1389,8 +1392,12 @@ static void dw_hdmi_bridge_mode_set(struct drm_bridge *bridge, > { > struct dw_hdmi *hdmi = bridge->driver_private; > > + mutex_lock(&hdmi->mutex); > + > /* Store the display mode for plugin/DKMS poweron events */ > memcpy(&hdmi->previous_mode, mode, sizeof(hdmi->previous_mode)); > + > + mutex_unlock(&hdmi->mutex); > } > > static bool dw_hdmi_bridge_mode_fixup(struct drm_bridge *bridge, > @@ -1404,14 +1411,20 @@ static void dw_hdmi_bridge_disable(struct drm_bridge *bridge) > { > struct dw_hdmi *hdmi = bridge->driver_private; > > + mutex_lock(&hdmi->mutex); > + hdmi->disabled = true; > dw_hdmi_poweroff(hdmi); > + mutex_unlock(&hdmi->mutex); > } > > static void dw_hdmi_bridge_enable(struct drm_bridge *bridge) > { > struct dw_hdmi *hdmi = bridge->driver_private; > > + mutex_lock(&hdmi->mutex); > dw_hdmi_poweron(hdmi); > + hdmi->disabled = false; > + mutex_unlock(&hdmi->mutex); > } > > static void dw_hdmi_bridge_nop(struct drm_bridge *bridge) > @@ -1534,20 +1547,20 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id) > phy_int_pol = hdmi_readb(hdmi, HDMI_PHY_POL0); > > if (intr_stat & HDMI_IH_PHY_STAT0_HPD) { > + hdmi_modb(hdmi, ~phy_int_pol, HDMI_PHY_HPD, HDMI_PHY_POL0); > + mutex_lock(&hdmi->mutex); > if (phy_int_pol & HDMI_PHY_HPD) { > dev_dbg(hdmi->dev, "EVENT=plugin\n"); > > - hdmi_modb(hdmi, 0, HDMI_PHY_HPD, HDMI_PHY_POL0); > - > - dw_hdmi_poweron(hdmi); > + if (!hdmi->disabled) > + dw_hdmi_poweron(hdmi); > } else { > dev_dbg(hdmi->dev, "EVENT=plugout\n"); > > - hdmi_modb(hdmi, HDMI_PHY_HPD, HDMI_PHY_HPD, > - HDMI_PHY_POL0); > - > - dw_hdmi_poweroff(hdmi); > + if (!hdmi->disabled) > + dw_hdmi_poweroff(hdmi); Just like my reply on 08/12, I thought this could be removed, so poweron/poweroff would only be called with bridge->enable/bridge->disable, them maybe no need mutex here. Best regards, - Yakir > } > + mutex_unlock(&hdmi->mutex); > drm_helper_hpd_irq_event(hdmi->bridge->dev); > } > > @@ -1617,7 +1630,9 @@ int dw_hdmi_bind(struct device *dev, struct device *master, > hdmi->sample_rate = 48000; > hdmi->ratio = 100; > hdmi->encoder = encoder; > + hdmi->disabled = true; > > + mutex_init(&hdmi->mutex); > mutex_init(&hdmi->audio_mutex); > spin_lock_init(&hdmi->audio_lock); > --------------070200020706080003070904 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 7bit

On 08/09/2015 12:04 AM, Russell King wrote:
The dw_hdmi enable/disable handling is particularly weak in several
regards:
* The hotplug interrupt could call hdmi_poweron() or hdmi_poweroff()
  while DRM is setting a mode, which could race with a mode being set.
* Hotplug will always re-enable the phy whenever it detects an active
  hotplug signal, even if DRM has disabled the output.

Resolve all of these by introducing a mutex to prevent races, and a
state-tracking bool so we know whether DRM wishes the output to be
enabled.  We choose to use our own mutex rather than ->struct_mutex
so that we can still process interrupts in a timely fashion.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 drivers/gpu/drm/bridge/dw_hdmi.c | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c
index 7b8a4e942a71..0ee188930d26 100644
--- a/drivers/gpu/drm/bridge/dw_hdmi.c
+++ b/drivers/gpu/drm/bridge/dw_hdmi.c
@@ -125,6 +125,9 @@ struct dw_hdmi {
 	bool sink_is_hdmi;
 	bool sink_has_audio;
 
+	struct mutex mutex;		/* for state below and previous_mode */
+	bool disabled;			/* DRM has disabled our bridge */
+
 	spinlock_t audio_lock;
 	struct mutex audio_mutex;
 	unsigned int sample_rate;
@@ -1389,8 +1392,12 @@ static void dw_hdmi_bridge_mode_set(struct drm_bridge *bridge,
 {
 	struct dw_hdmi *hdmi = bridge->driver_private;
 
+	mutex_lock(&hdmi->mutex);
+
 	/* Store the display mode for plugin/DKMS poweron events */
 	memcpy(&hdmi->previous_mode, mode, sizeof(hdmi->previous_mode));
+
+	mutex_unlock(&hdmi->mutex);
 }
 
 static bool dw_hdmi_bridge_mode_fixup(struct drm_bridge *bridge,
@@ -1404,14 +1411,20 @@ static void dw_hdmi_bridge_disable(struct drm_bridge *bridge)
 {
 	struct dw_hdmi *hdmi = bridge->driver_private;
 
+	mutex_lock(&hdmi->mutex);
+	hdmi->disabled = true;
 	dw_hdmi_poweroff(hdmi);
+	mutex_unlock(&hdmi->mutex);
 }
 
 static void dw_hdmi_bridge_enable(struct drm_bridge *bridge)
 {
 	struct dw_hdmi *hdmi = bridge->driver_private;
 
+	mutex_lock(&hdmi->mutex);
 	dw_hdmi_poweron(hdmi);
+	hdmi->disabled = false;
+	mutex_unlock(&hdmi->mutex);
 }
 
 static void dw_hdmi_bridge_nop(struct drm_bridge *bridge)
@@ -1534,20 +1547,20 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id)
 	phy_int_pol = hdmi_readb(hdmi, HDMI_PHY_POL0);
 
 	if (intr_stat & HDMI_IH_PHY_STAT0_HPD) {
+		hdmi_modb(hdmi, ~phy_int_pol, HDMI_PHY_HPD, HDMI_PHY_POL0);
+		mutex_lock(&hdmi->mutex);
 		if (phy_int_pol & HDMI_PHY_HPD) {
 			dev_dbg(hdmi->dev, "EVENT=plugin\n");
 
-			hdmi_modb(hdmi, 0, HDMI_PHY_HPD, HDMI_PHY_POL0);
-
-			dw_hdmi_poweron(hdmi);
+			if (!hdmi->disabled)
+				dw_hdmi_poweron(hdmi);
 		} else {
 			dev_dbg(hdmi->dev, "EVENT=plugout\n");
 
-			hdmi_modb(hdmi, HDMI_PHY_HPD, HDMI_PHY_HPD,
-				  HDMI_PHY_POL0);
-
-			dw_hdmi_poweroff(hdmi);
+			if (!hdmi->disabled)
+				dw_hdmi_poweroff(hdmi);

Just like my reply on 08/12, I thought this could be removed, so poweron/poweroff
would only be called with bridge->enable/bridge->disable, them maybe no need
mutex here.

Best regards,
- Yakir
 		}
+		mutex_unlock(&hdmi->mutex);
 		drm_helper_hpd_irq_event(hdmi->bridge->dev);
 	}
 
@@ -1617,7 +1630,9 @@ int dw_hdmi_bind(struct device *dev, struct device *master,
 	hdmi->sample_rate = 48000;
 	hdmi->ratio = 100;
 	hdmi->encoder = encoder;
+	hdmi->disabled = true;
 
+	mutex_init(&hdmi->mutex);
 	mutex_init(&hdmi->audio_mutex);
 	spin_lock_init(&hdmi->audio_lock);

--------------070200020706080003070904-- --===============0263446083== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Disposition: inline X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KZHJpLWRldmVs IG1haWxpbmcgbGlzdApkcmktZGV2ZWxAbGlzdHMuZnJlZWRlc2t0b3Aub3JnCmh0dHA6Ly9saXN0 cy5mcmVlZGVza3RvcC5vcmcvbWFpbG1hbi9saXN0aW5mby9kcmktZGV2ZWwK --===============0263446083==--