Alsa-Devel Archive on lore.kernel.org
 help / color / Atom feed
From: Russell King <rmk+kernel@arm.linux.org.uk>
To: alsa-devel@alsa-project.org, dri-devel@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org
Cc: Fabio Estevam <fabio.estevam@freescale.com>,
	David Airlie <airlied@linux.ie>, Mark Brown <broonie@kernel.org>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Yakir Yang <ykk@rock-chips.com>
Subject: [PATCH RFC 06/11] drm: bridge/dw_hdmi: introduce interfaces to enable and disable audio
Date: Mon, 30 Mar 2015 20:40:26 +0100
Message-ID: <E1YcfXu-0002v9-SB@rmk-PC.arm.linux.org.uk> (raw)
In-Reply-To: <20150330193911.GM24899@n2100.arm.linux.org.uk>

iMX6 devices from an errata (ERR005174) where the audio FIFO can be
emptied while it is partially full, resulting in misalignment of the
audio samples.

To prevent this, the errata workaround recommends writing N as zero
until the audio FIFO has been loaded by DMA.  Writing N=0 prevents the
HDMI bridge from reading from the audio FIFO, effectively disabling
audio.

This means we need to provide the audio driver with a pair of functions
to enable/disable audio.  These are dw_hdmi_audio_enable() and
dw_hdmi_audio_disable().

A spinlock is introduced to ensure that setting the CTS/N values can't
race, ensuring that the audio driver calling the enable/disable
functions (which are called in an atomic context) can't race with a
modeset.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 drivers/gpu/drm/bridge/dw_hdmi.c | 34 +++++++++++++++++++++++++++++++++-
 include/drm/bridge/dw_hdmi.h     |  2 ++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/dw_hdmi.c b/drivers/gpu/drm/bridge/dw_hdmi.c
index 245d17e58dec..67f07d15c12b 100644
--- a/drivers/gpu/drm/bridge/dw_hdmi.c
+++ b/drivers/gpu/drm/bridge/dw_hdmi.c
@@ -18,6 +18,7 @@
 #include <linux/hdmi.h>
 #include <linux/mutex.h>
 #include <linux/of_device.h>
+#include <linux/spinlock.h>
 
 #include <drm/drm_of.h>
 #include <drm/drmP.h>
@@ -124,8 +125,12 @@ struct dw_hdmi {
 	struct i2c_adapter *ddc;
 	void __iomem *regs;
 
+	spinlock_t audio_lock;
 	struct mutex audio_mutex;
 	unsigned int sample_rate;
+	unsigned int audio_cts;
+	unsigned int audio_n;
+	bool audio_enable;
 	int ratio;
 
 	void (*write)(struct dw_hdmi *hdmi, u8 val, int offset);
@@ -347,7 +352,11 @@ static void hdmi_set_clk_regenerator(struct dw_hdmi *hdmi,
 	dev_dbg(hdmi->dev, "%s: samplerate=%ukHz ratio=%d pixelclk=%luMHz N=%d cts=%d\n",
 		__func__, sample_rate, ratio, pixel_clk, n, cts);
 
-	hdmi_set_cts_n(hdmi, cts, n);
+	spin_lock_irq(&hdmi->audio_lock);
+	hdmi->audio_n = n;
+	hdmi->audio_cts = cts;
+	hdmi_set_cts_n(hdmi, cts, hdmi->audio_enable ? n : 0);
+	spin_unlock_irq(&hdmi->audio_lock);
 }
 
 static void hdmi_init_clk_regenerator(struct dw_hdmi *hdmi)
@@ -376,6 +385,28 @@ void dw_hdmi_set_sample_rate(struct dw_hdmi *hdmi, unsigned int rate)
 }
 EXPORT_SYMBOL_GPL(dw_hdmi_set_sample_rate);
 
+void dw_hdmi_audio_enable(struct dw_hdmi *hdmi)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&hdmi->audio_lock, flags);
+	hdmi->audio_enable = true;
+	hdmi_set_cts_n(hdmi, hdmi->audio_cts, hdmi->audio_n);
+	spin_unlock_irqrestore(&hdmi->audio_lock, flags);
+}
+EXPORT_SYMBOL_GPL(dw_hdmi_audio_enable);
+
+void dw_hdmi_audio_disable(struct dw_hdmi *hdmi)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&hdmi->audio_lock, flags);
+	hdmi->audio_enable = false;
+	hdmi_set_cts_n(hdmi, hdmi->audio_cts, 0);
+	spin_unlock_irqrestore(&hdmi->audio_lock, flags);
+}
+EXPORT_SYMBOL_GPL(dw_hdmi_audio_disable);
+
 /*
  * this submodule is responsible for the video data synchronization.
  * for example, for RGB 4:4:4 input, the data map is defined as
@@ -1579,6 +1610,7 @@ int dw_hdmi_bind(struct device *dev, struct device *master,
 	hdmi->encoder = encoder;
 
 	mutex_init(&hdmi->audio_mutex);
+	spin_lock_init(&hdmi->audio_lock);
 
 	of_property_read_u32(np, "reg-io-width", &val);
 
diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
index 424b51f6a215..ab5d36e83ea2 100644
--- a/include/drm/bridge/dw_hdmi.h
+++ b/include/drm/bridge/dw_hdmi.h
@@ -62,5 +62,7 @@ int dw_hdmi_bind(struct device *dev, struct device *master,
 		 const struct dw_hdmi_plat_data *plat_data);
 
 void dw_hdmi_set_sample_rate(struct dw_hdmi *hdmi, unsigned int rate);
+void dw_hdmi_audio_enable(struct dw_hdmi *hdmi);
+void dw_hdmi_audio_disable(struct dw_hdmi *hdmi);
 
 #endif /* __IMX_HDMI_H__ */
-- 
1.8.3.1

  parent reply index

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-30 19:39 [RFC 0/11] dw_hdmi cleanups, audio preparation, helpers and ahb audio support Russell King - ARM Linux
2015-03-30 19:40 ` [PATCH RFC 01/11] drm: bridge/dw_hdmi: clean up hdmi_set_clk_regenerator() Russell King
2015-03-31  6:55   ` Yang Kuankuan
2015-03-31 10:35     ` Russell King - ARM Linux
2015-04-01  1:54       ` Yakir
2015-03-30 19:40 ` [PATCH RFC 02/11] drm: bridge/dw_hdmi: use drm_hdmi_avi_infoframe_from_display_mode() Russell King
2015-03-31  9:02   ` Yang Kuankuan
2015-03-31 11:57     ` Russell King - ARM Linux
2015-04-01  1:31       ` Yakir
2015-03-30 19:40 ` [PATCH RFC 03/11] drm: bridge/dw_hdmi: simplify hdmi_config_AVI() a little Russell King
2015-03-30 19:40 ` [PATCH RFC 04/11] drm: bridge/dw_hdmi: remove mhsyncpolarity/mvsyncpolarity/minterlaced Russell King
2015-03-30 19:40 ` [PATCH RFC 05/11] drm: bridge/dw_hdmi: introduce interface to setting sample rate Russell King
2015-03-30 19:40 ` Russell King [this message]
2015-03-31  7:45   ` [PATCH RFC 06/11] drm: bridge/dw_hdmi: introduce interfaces to enable and disable audio Yang Kuankuan
2015-03-31  9:15   ` Philipp Zabel
2015-03-30 19:40 ` [PATCH RFC 07/11] drm/edid: add function to help find SADs Russell King
2015-04-01 11:47   ` Jani Nikula
2015-04-01 11:56     ` Russell King - ARM Linux
2015-04-02 10:52       ` [PATCH] drm/edid: add #defines for ELD versions Jani Nikula
2015-03-30 19:40 ` [PATCH RFC 08/11] sound/core: add DRM ELD helper Russell King
2015-03-31  9:12   ` Philipp Zabel
2015-03-30 19:40 ` [PATCH RFC 09/11] sound/core: add IEC958 channel status helper Russell King
2015-03-31  8:30   ` Yang Kuankuan
2015-03-31  9:13     ` Russell King - ARM Linux
2015-04-01  2:04       ` Yakir
2015-04-01  7:58         ` Russell King - ARM Linux
2015-03-31  9:10   ` Philipp Zabel
2015-03-31  9:16     ` Russell King - ARM Linux
2015-03-30 19:40 ` [PATCH RFC 10/11] drm: bridge/dw_hdmi-ahb-audio: add audio driver Russell King
2015-03-30 19:40 ` [PATCH RFC 11/11] drm: bridge/dw_hdmi-ahb-audio: parse ELD from HDMI driver Russell King

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=E1YcfXu-0002v9-SB@rmk-PC.arm.linux.org.uk \
    --to=rmk+kernel@arm.linux.org.uk \
    --cc=airlied@linux.ie \
    --cc=alsa-devel@alsa-project.org \
    --cc=broonie@kernel.org \
    --cc=dri-devel@lists.freedesktop.org \
    --cc=fabio.estevam@freescale.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=p.zabel@pengutronix.de \
    --cc=ykk@rock-chips.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Alsa-Devel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/alsa-devel/0 alsa-devel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 alsa-devel alsa-devel/ https://lore.kernel.org/alsa-devel \
		alsa-devel@alsa-project.org
	public-inbox-index alsa-devel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.alsa-project.alsa-devel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git