Re: [PATCH 2/2] ASoC: cs4270: add power management support

[Daniel Mack <daniel@caiaq.de>]

On Tue, May 05, 2009 at 10:30:48AM -0500, Timur Tabi wrote:
> > +static int cs4270_i2c_suspend(struct i2c_client *client, pm_message_t mesg)
> > +{
> > +	struct cs4270_private *cs4270 = i2c_get_clientdata(client);
> > +	struct snd_soc_codec *codec = &cs4270->codec;
> > +	int reg = snd_soc_read(codec, CS4270_PWRCTL);
> > +
> > +	if (reg < 0)
> > +		return reg;
> 
> You check for an error code from snd_soc_read() here, but ...
> 
> > +	/* ... then disable the power-down bits */
> > +	reg = snd_soc_read(codec, CS4270_PWRCTL);
> 
> you don't check for it here.
> 
> In cs4270_i2c_suspend(), snd_soc_read() can never return an error,
> because you're passing a hard-coded register address.

Ok - see the patch below.

Thanks,
Daniel


>From d2303f37695145018e07aad85200f06b24341648 Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@caiaq.de>
Date: Thu, 2 Apr 2009 15:43:44 +0200
Subject: [PATCH 2/2] ASoC: cs4270: add power management support

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Cc: Timur Tabi <timur@freescale.com>
Cc: Mark Brown <broonie@sirena.org.uk>
---
 sound/soc/codecs/cs4270.c |   59 ++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 58 insertions(+), 1 deletions(-)

diff --git a/sound/soc/codecs/cs4270.c b/sound/soc/codecs/cs4270.c
index bc338df..65c68a0 100644
--- a/sound/soc/codecs/cs4270.c
+++ b/sound/soc/codecs/cs4270.c
@@ -18,7 +18,7 @@
  * - The machine driver's 'startup' function must call
  *   cs4270_set_dai_sysclk() with the value of MCLK.
  * - Only I2S and left-justified modes are supported
- * - Power management is not supported
+ * - Power management is supported
  */
 
 #include <linux/module.h>
@@ -27,6 +27,7 @@
 #include <sound/soc.h>
 #include <sound/initval.h>
 #include <linux/i2c.h>
+#include <linux/delay.h>
 
 #include "cs4270.h"
 
@@ -65,6 +66,8 @@
 #define CS4270_PWRCTL_PDN_ADC	0x20
 #define CS4270_PWRCTL_PDN_DAC	0x02
 #define CS4270_PWRCTL_PDN	0x01
+#define CS4270_PWRCTL_PDN_ALL	\
+	(CS4270_PWRCTL_PDN_ADC | CS4270_PWRCTL_PDN_DAC | CS4270_PWRCTL_PDN)
 #define CS4270_MODE_SPEED_MASK	0x30
 #define CS4270_MODE_1X		0x00
 #define CS4270_MODE_2X		0x10
@@ -788,6 +791,58 @@ static struct i2c_device_id cs4270_id[] = {
 };
 MODULE_DEVICE_TABLE(i2c, cs4270_id);
 
+#ifdef CONFIG_PM
+
+/* This suspend/resume implementation can handle both - a simple standby
+ * where the codec remains powered, and a full suspend, where the voltage
+ * domain the codec is connected to is teared down and/or any other hardware
+ * reset condition is asserted.
+ *
+ * The codec's own power saving features are enabled in the suspend callback,
+ * and all registers are written back to the hardware when resuming.
+ */
+
+static int cs4270_i2c_suspend(struct i2c_client *client, pm_message_t mesg)
+{
+	struct cs4270_private *cs4270 = i2c_get_clientdata(client);
+	struct snd_soc_codec *codec = &cs4270->codec;
+	int reg = snd_soc_read(codec, CS4270_PWRCTL) | CS4270_PWRCTL_PDN_ALL;
+	return snd_soc_write(codec, CS4270_PWRCTL, reg);
+}
+
+static int cs4270_i2c_resume(struct i2c_client *client)
+{
+	struct cs4270_private *cs4270 = i2c_get_clientdata(client);
+	struct snd_soc_codec *codec = &cs4270->codec;
+	int reg;
+
+	/* In case the device was put to hard reset during sleep, we need to
+	 * wait 500ns here before any I2C communication. */
+	ndelay(500);
+
+	/* first restore the entire register cache ... */
+	for (reg = CS4270_FIRSTREG; reg <= CS4270_LASTREG; reg++) {
+		u8 val = snd_soc_read(codec, reg);
+
+		if (i2c_smbus_write_byte_data(client, reg, val)) {
+			dev_err(codec->dev, "i2c write failed\n");
+			return -EIO;
+		}
+	}
+
+	/* ... then disable the power-down bits */
+	reg = snd_soc_read(codec, CS4270_PWRCTL);
+	if (reg < 0)
+		return reg;
+
+	reg &= ~CS4270_PWRCTL_PDN_ALL;
+	return snd_soc_write(codec, CS4270_PWRCTL, reg);
+}
+#else
+#define cs4270_i2c_suspend	NULL
+#define cs4270_i2c_resume	NULL
+#endif /* CONFIG_PM */
+
 /*
  * cs4270_i2c_driver - I2C device identification
  *
@@ -802,6 +857,8 @@ static struct i2c_driver cs4270_i2c_driver = {
 	.id_table = cs4270_id,
 	.probe = cs4270_i2c_probe,
 	.remove = cs4270_i2c_remove,
+	.suspend = cs4270_i2c_suspend,
+	.resume = cs4270_i2c_resume,
 };
 
 /*
-- 
1.6.2.1