linux-kernel - [PATCH 3.16.y-ckt 20/58] ASoC: sgtl5000: add delay before first I2C access

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Message-Id: <1424353948-31863-21-git-send-email-luis.henriques@canonical.com>
Date:	Thu, 19 Feb 2015 13:51:50 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Eric Nelson <eric.nelson@...ndarydevices.com>,
	Mark Brown <broonie@...nel.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 20/58] ASoC: sgtl5000: add delay before first I2C access

3.16.7-ckt7 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Nelson <eric.nelson@...ndarydevices.com>

commit 58cc9c9a175885bbf6bae3acf18233d0a8229a84 upstream.

To quote from section 1.3.1 of the data sheet:
	The SGTL5000 has an internal reset that is deasserted
	8 SYS_MCLK cycles after all power rails have been brought
	up. After this time, communication can start

	...
	1.0us represents 8 SYS_MCLK cycles at the minimum 8.0 MHz SYS_MCLK.

Signed-off-by: Eric Nelson <eric.nelson@...ndarydevices.com>
Reviewed-by: Fabio Estevam <fabio.estevam@...escale.com>
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 sound/soc/codecs/sgtl5000.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/soc/codecs/sgtl5000.c b/sound/soc/codecs/sgtl5000.c
index f039d668266e..a62d340aa98a 100644
--- a/sound/soc/codecs/sgtl5000.c
+++ b/sound/soc/codecs/sgtl5000.c
@@ -1463,6 +1463,9 @@ static int sgtl5000_i2c_probe(struct i2c_client *client,
 	if (ret)
 		return ret;
 
+	/* Need 8 clocks before I2C accesses */
+	udelay(1);
+
 	/* read chip information */
 	ret = regmap_read(sgtl5000->regmap, SGTL5000_CHIP_ID, &reg);
 	if (ret)
-- 
2.1.4

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